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Sample records for sauropodomorph dinosauria saurischia

  1. New stem-sauropodomorph (Dinosauria, Saurischia) from the Triassic of Brazil

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    Cabreira, Sergio F.; Schultz, Cesar L.; Bittencourt, Jonathas S.; Soares, Marina B.; Fortier, Daniel C.; Silva, Lúcio R.; Langer, Max C.

    2011-12-01

    Post-Triassic theropod, sauropodomorph, and ornithischian dinosaurs are readily recognized based on the set of traits that typically characterize each of these groups. On the contrary, most of the early members of those lineages lack such specializations, but share a range of generalized traits also seen in more basal dinosauromorphs. Here, we report on a new Late Triassic dinosaur from the Santa Maria Formation of Rio Grande do Sul, southern Brazil. The specimen comprises the disarticulated partial skeleton of a single individual, including most of the skull bones. Based on four phylogenetic analyses, the new dinosaur fits consistently on the sauropodomorph stem, but lacks several typical features of sauropodomorphs, showing dinosaur plesiomorphies together with some neotheropod traits. This is not an exception among basal dinosaurs, the early radiation of which is characterized by a mosaic pattern of character acquisition, resulting in the uncertain phylogenetic placement of various early members of the group.

  2. A basal sauropodomorph (Dinosauria: Saurischia from the Ischigualasto Formation (Triassic, Carnian and the early evolution of Sauropodomorpha.

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    Ricardo N Martinez

    Full Text Available BACKGROUND: The earliest dinosaurs are from the early Late Triassic (Carnian of South America. By the Carnian the main clades Saurischia and Ornithischia were already established, and the presence of the most primitive known sauropodomorph Saturnalia suggests also that Saurischia had already diverged into Theropoda and Sauropodomorpha. Knowledge of Carnian sauropodomorphs has been restricted to this single species. METHODOLOGY/PRINCIPAL FINDINGS: We describe a new small sauropodomorph dinosaur from the Ischigualsto Formation (Carnian in northwest Argentina, Panphagia protos gen. et sp. nov., on the basis of a partial skeleton. The genus and species are characterized by an anteroposteriorly elongated fossa on the base of the anteroventral process of the nasal; wide lateral flange on the quadrate with a large foramen; deep groove on the lateral surface of the lower jaw surrounded by prominent dorsal and ventral ridges; bifurcated posteroventral process of the dentary; long retroarticular process transversally wider than the articular area for the quadrate; oval scars on the lateral surface of the posterior border of the centra of cervical vertebrae; distinct prominences on the neural arc of the anterior cervical vertebra; distal end of the scapular blade nearly three times wider than the neck; scapular blade with an expanded posterodistal corner; and medial lamina of brevis fossa twice as wide as the iliac spine. CONCLUSIONS/SIGNIFICANCE: We regard Panphagia as the most basal sauropodomorph, which shares the following apomorphies with Saturnalia and more derived sauropodomorphs: basally constricted crowns; lanceolate crowns; teeth of the anterior quarter of the dentary higher than the others; and short posterolateral flange of distal tibia. The presence of Panphagia at the base of the early Carnian Ischigualasto Formation suggests an earlier origin of Sauropodomorpha during the Middle Triassic.

  3. A new basal sauropodomorph (Dinosauria: Saurischia from Quebrada del Barro Formation (Marayes-El Carrizal Basin, northwestern Argentina.

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    Cecilia Apaldetti

    Full Text Available BACKGROUND: Argentinean basal sauropodomorphs are known by several specimens from different basins; Ischigualasto, El Tranquilo, and Mogna. The Argentinean record is diverse and includes some of the most primitive known sauropodomorphs such as Panphagia and Chromogisaurus, as well as more derived forms, including several massospondylids. Until now, the Massospondylidae were the group of basal sauropodomorphs most widely spread around Pangea with a record in almost all continents, mostly from the southern hemisphere, including the only record from Antarctica. METHODOLOGY/PRINCIPAL FINDING: We describe here a new basal sauropodomorph, Leyesaurus marayensis gen. et sp. nov., from the Quebrada del Barro Formation, an Upper Triassic-Lower Jurassic unit that crops out in northwestern Argentina. The new taxon is represented by a partial articulated skeleton that includes the skull, vertebral column, scapular and pelvic girdles, and hindlimb. Leyesaurus is diagnosed by a set of unique features, such as a sharply acute angle (50 degrees formed by the ascending process of the maxilla and the alveolar margin, a straight ascending process of the maxilla with a longitudinal ridge on its lateral surface, noticeably bulging labial side of the maxillary teeth, greatly elongated cervical vertebrae, and proximal articular surface of metatarsal III that is shelf-like and medially deflected. Phylogenetic analysis recovers Leyesaurus as a basal sauropodomorph, sister taxon of Adeopapposaurus within the Massospondylidae. Moreover, the results suggest that massospondylids achieved a higher diversity than previously thought. CONCLUSIONS/SIGNIFICANCE: Our phylogenetic results differ with respect to previous analyses by rejecting the massospondylid affinities of some taxa from the northern hemisphere (e.g., Seitaad, Sarahsaurus. As a result, the new taxon Leyesaurus, coupled with other recent discoveries, suggests that the diversity of massospondylids in the southern

  4. A New Basal Sauropodomorph (Dinosauria: Saurischia) from Quebrada del Barro Formation (Marayes-El Carrizal Basin), Northwestern Argentina

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    Apaldetti, Cecilia; Martinez, Ricardo N.; Alcober, Oscar A.; Pol, Diego

    2011-01-01

    Background Argentinean basal sauropodomorphs are known by several specimens from different basins; Ischigualasto, El Tranquilo, and Mogna. The Argentinean record is diverse and includes some of the most primitive known sauropodomorphs such as Panphagia and Chromogisaurus, as well as more derived forms, including several massospondylids. Until now, the Massospondylidae were the group of basal sauropodomorphs most widely spread around Pangea with a record in almost all continents, mostly from the southern hemisphere, including the only record from Antarctica. Methodology/Principal Finding We describe here a new basal sauropodomorph, Leyesaurus marayensis gen. et sp. nov., from the Quebrada del Barro Formation, an Upper Triassic-Lower Jurassic unit that crops out in northwestern Argentina. The new taxon is represented by a partial articulated skeleton that includes the skull, vertebral column, scapular and pelvic girdles, and hindlimb. Leyesaurus is diagnosed by a set of unique features, such as a sharply acute angle (50 degrees) formed by the ascending process of the maxilla and the alveolar margin, a straight ascending process of the maxilla with a longitudinal ridge on its lateral surface, noticeably bulging labial side of the maxillary teeth, greatly elongated cervical vertebrae, and proximal articular surface of metatarsal III that is shelf-like and medially deflected. Phylogenetic analysis recovers Leyesaurus as a basal sauropodomorph, sister taxon of Adeopapposaurus within the Massospondylidae. Moreover, the results suggest that massospondylids achieved a higher diversity than previously thought. Conclusions/Significance Our phylogenetic results differ with respect to previous analyses by rejecting the massospondylid affinities of some taxa from the northern hemisphere (e.g., Seitaad, Sarahsaurus). As a result, the new taxon Leyesaurus, coupled with other recent discoveries, suggests that the diversity of massospondylids in the southern hemisphere was higher

  5. Pelvic and hind limb musculature of Staurikosaurus pricei (Dinosauria: Saurischia

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    Orlando N. Grillo

    2011-03-01

    Full Text Available The study of pelvic and hind limb bones and muscles in basal dinosaurs is important for understanding the early evolution of bipedal locomotion in the group. The use of data from both extant and extinct taxa placed into a phylogenetic context allowed to make well-supported inferences concerning most of the hind limb musculature of the basal saurischian Staurikosaurus pricei Colbert, 1970 (Santa Maria Formation, Late Triassic of Rio Grande do Sul, Brazil. Two large concavities in the lateral surface of the ilium represent the origin of the muscles iliotrochantericus caudalis plus iliofemoralis externus (in the anterior concavity and iliofibularis (in the posterior concavity. Muscle ambiens has only one head and originates from the pubic tubercle. The origin of puboischiofemoralis internus 1 possibly corresponds to a fossa in the ventral margin of the pré-acetabular iliac process. This could represent an intermediate stage prior to the origin of a true pré-acetabular fossa. Muscles caudofemorales longus et brevis were likely well developed, and Staurikosaurus is unique in bearing a posteriorly projected surface for the origin of caudofemoralis brevis.O estudo da musculatura pelvica e do membro posterior em dinossauros basais e importante para entender a evolução inicial do bipedalismo em dinossauros Saurischia. Empregando uma metodologia que tem como base dados obtidos a partir de taxons viventes e extintos posicionados em um contexto filogenetico, foi possivel fazer inferencias bem suportadas relativas a maior parte dos musculos do membro posterior do dinossauro Saurischia basal Staurikosaurus pricei Colbert, 1970 (Formação Santa Maria, Triassico Superior do Rio Grande do Sul, Brasil. Duas grandes concavidades na superficie lateral do ilio correspondem a origem dos musculos iliotrochantericus caudalis e iliofeoralis externus (compartilhando a concavidade anterior e para o musculo iliofibularis (na concavidade posterior. O musculo ambiens

  6. Unusual endosteally formed bone tissue in a patagonian basal sauropodomorph dinosaur.

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    Cerda, Ignacio A; Chinsamy, Anusuya; Pol, Diego

    2014-08-01

    Mussaurus patagonicus (Dinosauria: Sauropodomorpha) is a basal sauropodomorph from the Late Triassic of southern Argentina that is known from a large number of individuals, including juveniles, subadults, and adults. Here, we report on the occurrence of an unusual bone tissue in an individual of M. patagonicus. The rather atypical bone tissue is located within the femoral medullary cavity and also occurs within several erosion cavities of the midinner part of the cortex. This tissue is well vascularized and is composed of a matrix that consists of abundant and densely packed osteocyte lacunae. Although some features of this tissue resembles avian medullary bone, the histological features are distinctive and share more features with the pathological, reactive bone produced in extant birds in response to a retrovirus-induced disease (avian osteopetrosis). Here, we also discuss and provide histological features to effectively differentiate endosteally formed medullary bone from pathological avian osteopetrosis. Copyright © 2014 Wiley Periodicals, Inc.

  7. First sauropod (Dinosauria: Saurischia) remains from the Guichón Formation, Late Cretaceous of Uruguay

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    Soto, Matías; Perea, Daniel; Cambiaso, Andrea

    2012-02-01

    We report the first sauropod remains recorded in the Guichón Formation, western Uruguay. The materials belong to a middle-sized sauropod represented by more than one individual, and among other remains include more than fifty caudal centra. Close to the bones, several eggshell fragments resembling Sphaerovum erbeniMones, 1980 were found. We discuss the biostratigraphic implications of these findings, which for the first time allow us to confidently refer the Guichón Formation to the Late Cretaceous. The combination of several synapomorphies such as a biconvex first caudal centrum, strongly procoelous middle and distal caudal centra, and a pyramidal astragalus suggests that the sauropod remains belong to a derived lithostrotian, probably related to Pellegrinisaurus powelli, Baurutitan britoi and Alamosaurus sanjuanensis. A few isolated teeth (now lost) referred by Frederich von Huene in 1934 to ornithomimid theropods and ornithischians are herein reinterpreted as belonging to indeterminate theropods and basal iguanodontians.

  8. The sauropodomorph biostratigraphy of the Elliot Formation of southern Africa: Tracking the evolution of Sauropodomorpha across the Triassic–Jurassic boundary

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    Blair W. McPhee

    2017-09-01

    Full Text Available The latest Triassic is notable for coinciding with the dramatic decline of many previously dominant groups, followed by the rapid radiation of Dinosauria in the Early Jurassic. Among the most common terrestrial vertebrates from this time, sauropodomorph dinosaurs provide an important insight into the changing dynamics of the biota across the Triassic–Jurassic boundary. The Elliot Formation of South Africa and Lesotho preserves the richest assemblage of sauropodomorphs known from this age, and is a key index assemblage for biostratigraphic correlations with other similarly-aged global terrestrial deposits. Past assessments of Elliot Formation biostratigraphy were hampered by an overly simplistic biozonation scheme which divided it into a lower “Euskelosaurus” Range Zone and an upper Massospondylus Range Zone. Here we revise the zonation of the Elliot Formation by: (i synthesizing the last three decades’ worth of fossil discoveries, taxonomic revision, and lithostratigraphic investigation; and (ii systematically reappraising the stratigraphic provenance of important fossil locations. We then use our revised stratigraphic information in conjunction with phylogenetic character data to assess morphological disparity between Late Triassic and Early Jurassic sauropodomorph taxa. Our results demonstrate that the Early Jurassic upper Elliot Formation is considerably more taxonomically and morphologically diverse than previously thought. In contrast, the sauropodomorph fauna of the Late Triassic lower Elliot Formation remains relatively poorly understood due to the pervasive incompleteness of many key specimens, as well as the relative homogeneity of their diagnostic character suites. Our metrics indicate that both Elliot Formation and global sauropodomorph assemblages had greater morphological disparity within the Early Jurassic than the Late Triassic. This result is discussed in the context of changing palaeoclimatic conditions, as well as

  9. New material and revision of Melanorosaurus thabanensis, a basal sauropodomorph from the Upper Triassic of Lesotho.

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    Peyre de Fabrègues, Claire; Allain, Ronan

    2016-01-01

    Melanorosaurus is a genus of basal sauropodomorph that currently includes two species from Southern Africa. In this paper, we redescribe the holotype femur of Melanorosaurus thabanensis from the Elliot Formation of Lesotho, as well as associated remains. The stratigraphic position of this taxon is reviewed, and it is clear that it comes from the Lower Elliot Formation being, therefore, Late Triassic in age, and not Early Jurassic as originally described. The knowledge of the anatomy of the basal sauropodomorph of Thabana Morena is enhanced by the description of six new skeletal elements from the type locality. The femur and the ilium from Thabana Morena are diagnostic and characterized by unusual proportions. The first phylogenetic analysis including both this specimen and Melanorosaurus is conducted. This analysis leads to the conclusion that the femur described in the original publication of Melanorosaurus thabanensis can no longer be referred to Melanorosaurus. For these reasons, we hereby create Meroktenos gen. nov. to encompass Meroktenos thabanensis comb. nov.

  10. Functional and biomechanic aspects of the scapular girdle and forelimbs of Unaysaurus tolentinoiLeal et al., 2004 (Saurischia: Sauropodomorpha)

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    Vargas-Peixoto, Dilson; Da-Rosa, Átila Augusto Stock; Gallo de França, Marco Aurélio

    2015-08-01

    This study presents evidence about the biomechanics and forelimbs functionality of the basal sauropodomorph Unaysaurus tolentinoi (upper portion of the SM2 sequence, Santa Maria Supersequence, Upper Triassic from southern Brazil). Maximum and minimum motion angles were inferred in the joints, disregarding the presence and/or thickness of cartilage. Furthermore, processes and external structures of the bones were analyzed in attributing the functionality of forelimbs. Unaysaurus tolentinoi had well-developed grapple ability. However, the preserved elements and their osteological features are not conclusive about strictly bipedalism or quadrupedalism in U. tolentinoi.

  11. Dispersal and diversity in the earliest North American sauropodomorph dinosaurs, with a description of a new taxon.

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    Rowe, Timothy B; Sues, Hans-Dieter; Reisz, Robert R

    2011-04-07

    Sauropodomorph dinosaurs originated in the Southern Hemisphere in the Middle or Late Triassic and are commonly portrayed as spreading rapidly to all corners of Pangaea as part of a uniform Late Triassic to Early Jurassic cosmopolitan dinosaur fauna. Under this model, dispersal allegedly inhibited dinosaurian diversification, while vicariance and local extinction enhanced it. However, apomorphy-based analyses of the known fossil record indicate that sauropodomorphs were absent in North America until the Early Jurassic, reframing the temporal context of their arrival. We describe a new taxon from the Kayenta Formation of Arizona that comprises the third diagnosable sauropodomorph from the Early Jurassic of North America. We analysed its relationships to test whether sauropodomorphs reached North America in a single sweepstakes event or in separate dispersals. Our finding of separate arrivals by all three taxa suggests dispersal as a chief factor in dinosaurian diversification during at least the early Mesozoic. It questions whether a 'cosmopolitan' dinosaur fauna ever existed, and corroborates that vicariance, extinction and dispersal did not operate uniformly in time or under uniform conditions during the Mesozoic. Their relative importance is best measured in narrow time slices and circumscribed geographical regions.

  12. Sauropodomorph dinosaur trackways from the Fleming Fjord Formation of East Greenland: Evidence for Late Triassic sauropods

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    Jens N. Lallensack

    2017-11-01

    Full Text Available The Late Triassic (Norian–early Rhaetian Fleming Fjord Formation of central East Greenland preserves a diverse fossil fauna, including both body and trace fossils. Trackways of large quadrupedal archosaurs, although already reported in 1994 and mentioned in subsequent publications, are here described and figured in detail for the first time, based on photogrammetric data collected during fieldwork in 2012. Two trackways can be referred to Eosauropus, while a third, bipedal trackway may be referred to Evazoum, both of which have been considered to represent sauropodomorph dinosaur tracks. Both the Evazoum and the Eosauropus trackways are distinctly larger than other trackways referred to the respective ichnogenera. The trackmaker of the best preserved Eosauropus trackway is constrained using a synapomorphy-based approach. The quadrupedal posture, the entaxonic pes structure, and five weight-bearing digits indicate a derived sauropodiform trackmaker. Other features exhibited by the tracks, including the semi-digitigrade pes and the laterally deflected unguals, are commonly considered synapomorphies of more exclusive clades within Sauropoda. The present trackway documents an early acquisition of a eusauropod-like pes anatomy while retaining a well-developed claw on pedal digit IV, which is reduced in eusauropods. Although unequivocal evidence for sauropod dinosaurs is no older than the Early Jurassic, the present trackway provides evidence for a possible Triassic origin of the group.

  13. A hyper-robust sauropodomorph dinosaur ilium from the Upper Triassic-Lower Jurassic Elliot Formation of South Africa: Implications for the functional diversity of basal Sauropodomorpha

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    McPhee, Blair W.; Choiniere, Jonah N.

    2016-11-01

    It has generally been held that the locomotory habits of sauropodomorph dinosaurs moved in a relatively linear evolutionary progression from bipedal through "semi-bipedal" to the fully quadrupedal gait of Sauropoda. However, there is now a growing appreciation of the range of locomotory strategies practiced amongst contemporaneous taxa of the latest Triassic and earliest Jurassic. Here we present on the anatomy of a hyper-robust basal sauropodomorph ilium from the Late Triassic-Early Jurassic Elliot Formation of South Africa. This element, in addition to highlighting the unexpected range of bauplan diversity throughout basal Sauropodomorpha, also has implications for our understanding of the relevance of "robusticity" to sauropodomorph evolution beyond generalized limb scaling relationships. Possibly representing a unique form of hindlimb stabilization during phases of bipedal locomotion, the autapomorphic morphology of this newly rediscovered ilium provides additional insight into the myriad ways in which basal Sauropodomorpha managed the inherited behavioural and biomechanical challenges of increasing body-size, hyper-herbivory, and a forelimb primarily adapted for use in a bipedal context.

  14. Testing the effect of the rock record on diversity: a multidisciplinary approach to elucidating the generic richness of sauropodomorph dinosaurs through time.

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    Mannion, Philip D; Upchurch, Paul; Carrano, Matthew T; Barrett, Paul M

    2011-02-01

    The accurate reconstruction of palaeobiodiversity patterns is central to a detailed understanding of the macroevolutionary history of a group of organisms. However, there is increasing evidence that diversity patterns observed directly from the fossil record are strongly influenced by fluctuations in the quality of our sampling of the rock record; thus, any patterns we see may reflect sampling biases, rather than genuine biological signals. Previous dinosaur diversity studies have suggested that fluctuations in sauropodomorph palaeobiodiversity reflect genuine biological signals, in comparison to theropods and ornithischians whose diversity seems to be largely controlled by the rock record. Most previous diversity analyses that have attempted to take into account the effects of sampling biases have used only a single method or proxy: here we use a number of techniques in order to elucidate diversity. A global database of all known sauropodomorph body fossil occurrences (2024) was constructed. A taxic diversity curve for all valid sauropodomorph genera was extracted from this database and compared statistically with several sampling proxies (rock outcrop area and dinosaur-bearing formations and collections), each of which captures a different aspect of fossil record sampling. Phylogenetic diversity estimates, residuals and sample-based rarefaction (including the first attempt to capture 'cryptic' diversity in dinosaurs) were implemented to investigate further the effects of sampling. After 'removal' of biases, sauropodomorph diversity appears to be genuinely high in the Norian, Pliensbachian-Toarcian, Bathonian-Callovian and Kimmeridgian-Tithonian (with a small peak in the Aptian), whereas low diversity levels are recorded for the Oxfordian and Berriasian-Barremian, with the Jurassic/Cretaceous boundary seemingly representing a real diversity trough. Observed diversity in the remaining Triassic-Jurassic stages appears to be largely driven by sampling effort. Late

  15. Aging, Maturation and Growth of Sauropodomorph Dinosaurs as Deduced from Growth Curves Using Long Bone Histological Data: An Assessment of Methodological Constraints and Solutions.

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    Griebeler, Eva Maria; Klein, Nicole; Sander, P Martin

    2013-01-01

    Information on aging, maturation, and growth is important for understanding life histories of organisms. In extinct dinosaurs, such information can be derived from the histological growth record preserved in the mid-shaft cortex of long bones. Here, we construct growth models to estimate ages at death, ages at sexual maturity, ages at which individuals were fully-grown, and maximum growth rates from the growth record preserved in long bones of six sauropod dinosaur individuals (one indeterminate mamenchisaurid, two Apatosaurus sp., two indeterminate diplodocids, and one Camarasaurus sp.) and one basal sauropodomorph dinosaur individual (Plateosaurus engelhardti). Using these estimates, we establish allometries between body mass and each of these traits and compare these to extant taxa. Growth models considered for each dinosaur individual were the von Bertalanffy model, the Gompertz model, and the logistic model (LGM), all of which have inherently fixed inflection points, and the Chapman-Richards model in which the point is not fixed. We use the arithmetic mean of the age at the inflection point and of the age at which 90% of asymptotic mass is reached to assess respectively the age at sexual maturity or the age at onset of reproduction, because unambiguous indicators of maturity in Sauropodomorpha are lacking. According to an AIC-based model selection process, the LGM was the best model for our sauropodomorph sample. Allometries established are consistent with literature data on other Sauropodomorpha. All Sauropodomorpha reached full size within a time span similar to scaled-up modern mammalian megaherbivores and had similar maximum growth rates to scaled-up modern megaherbivores and ratites, but growth rates of Sauropodomorpha were lower than of an average mammal. Sauropodomorph ages at death probably were lower than that of average scaled-up ratites and megaherbivores. Sauropodomorpha were older at maturation than scaled-up ratites and average mammals, but

  16. A new sauropodomorph dinosaur from the Early Jurassic of Patagonia and the origin and evolution of the sauropod-type sacrum.

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    Diego Pol

    Full Text Available BACKGROUND: The origin of sauropod dinosaurs is one of the major landmarks of dinosaur evolution but is still poorly understood. This drastic transformation involved major skeletal modifications, including a shift from the small and gracile condition of primitive sauropodomorphs to the gigantic and quadrupedal condition of sauropods. Recent findings in the Late Triassic-Early Jurassic of Gondwana provide critical evidence to understand the origin and early evolution of sauropods. METHODOLOGY/PRINCIPAL FINDINGS: A new sauropodomorph dinosaur, Leonerasaurus taquetrensis gen. et sp. nov., is described from the Las Leoneras Formation of Central Patagonia (Argentina. The new taxon is diagnosed by the presence of anterior unserrated teeth with a low spoon-shaped crown, amphicoelous and acamerate vertebral centra, four sacral vertebrae, and humeral deltopectoral crest low and medially deflected along its distal half. The phylogenetic analysis depicts Leonerasaurus as one of the closest outgroups of Sauropoda, being the sister taxon of a clade of large bodied taxa composed of Melanorosaurus and Sauropoda. CONCLUSIONS/SIGNIFICANCE: The dental and postcranial anatomy of Leonerasaurus supports its close affinities with basal sauropods. Despite the small size and plesiomorphic skeletal anatomy of Leonerasaurus, the four vertebrae that compose its sacrum resemble that of the large-bodied primitive sauropods. This shows that the appearance of the sauropod-type of sacrum predated the marked increase in body size that characterizes the origins of sauropods, rejecting a causal explanation and evolutionary linkage between this sacral configuration and body size. Alternative phylogenetic placements of Leonerasaurus as a basal anchisaurian imply a convergent acquisition of the sauropod-type sacrum in the new small-bodied taxon, also rejecting an evolutionary dependence of sacral configuration and body size in sauropodomorphs. This and other recent discoveries are

  17. Aging, Maturation and Growth of Sauropodomorph Dinosaurs as Deduced from Growth Curves Using Long Bone Histological Data: An Assessment of Methodological Constraints and Solutions.

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    Eva Maria Griebeler

    Full Text Available Information on aging, maturation, and growth is important for understanding life histories of organisms. In extinct dinosaurs, such information can be derived from the histological growth record preserved in the mid-shaft cortex of long bones. Here, we construct growth models to estimate ages at death, ages at sexual maturity, ages at which individuals were fully-grown, and maximum growth rates from the growth record preserved in long bones of six sauropod dinosaur individuals (one indeterminate mamenchisaurid, two Apatosaurus sp., two indeterminate diplodocids, and one Camarasaurus sp. and one basal sauropodomorph dinosaur individual (Plateosaurus engelhardti. Using these estimates, we establish allometries between body mass and each of these traits and compare these to extant taxa. Growth models considered for each dinosaur individual were the von Bertalanffy model, the Gompertz model, and the logistic model (LGM, all of which have inherently fixed inflection points, and the Chapman-Richards model in which the point is not fixed. We use the arithmetic mean of the age at the inflection point and of the age at which 90% of asymptotic mass is reached to assess respectively the age at sexual maturity or the age at onset of reproduction, because unambiguous indicators of maturity in Sauropodomorpha are lacking. According to an AIC-based model selection process, the LGM was the best model for our sauropodomorph sample. Allometries established are consistent with literature data on other Sauropodomorpha. All Sauropodomorpha reached full size within a time span similar to scaled-up modern mammalian megaherbivores and had similar maximum growth rates to scaled-up modern megaherbivores and ratites, but growth rates of Sauropodomorpha were lower than of an average mammal. Sauropodomorph ages at death probably were lower than that of average scaled-up ratites and megaherbivores. Sauropodomorpha were older at maturation than scaled-up ratites and average

  18. A new basal sauropod from the pre-Toarcian Jurassic of South Africa: evidence of niche-partitioning at the sauropodomorph-sauropod boundary?

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    McPhee, Blair W; Bonnan, Matthew F; Yates, Adam M; Neveling, Johann; Choiniere, Jonah N

    2015-08-19

    The early evolution of sauropod dinosaurs remains poorly understood, with a paucity of unequivocal sauropod taxa known from the first twenty million years of the Jurassic. Recently, the Early Jurassic of South Africa has yielded an assemblage of dental and post-cranial remains displaying a more apomorphic character suite than any other similarly aged sauropodomorph. These remains are interpreted as a new species of basal sauropod and recovered cladistically as the sister taxon to Vulcanodon +more derived Sauropoda, underscoring its importance for our understanding of this pivotal period of sauropod evolution. Key changes in the dentition, axial skeleton and forelimb of this new species suggest a genuine functional distinction occurring at the sauropodiform-sauropod boundary. With reference to these changes, we propose a scenario in which interdependent refinements of the locomotory and feeding apparatus occurred in tandem with, or were effected by, restrictions in the amount of vertical forage initially available to the earliest sauropods. The hypothesized instance of niche-partitioning between basal sauropodan taxa and higher-browsing non-sauropodan sauropodomorphs may partially explain the rarity of true sauropods in the basal rocks of the Jurassic, while having the added corollary of couching the origins of Sauropoda in terms of an ecologically delimited 'event'.

  19. The first juvenile specimens of Plateosaurus engelhardti from Frick, Switzerland: isolated neural arches and their implications for developmental plasticity in a basal sauropodomorph

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    Rebecca Hofmann

    2014-07-01

    Full Text Available The dinosaur Plateosaurus engelhardti is the most abundant dinosaur in the Late Triassic of Europe and the best known basal sauropodomorph. Plateosaurus engelhardti was one of the first sauropodomorph dinosaurs to display a large body size. Remains can be found in the Norian stage of the Late Triassic in over 40 localities in Central Europe (France, Germany, and Switzerland and in Greenland. Since the first discovery of P. engelhardti no juvenile specimens of this species had been described in detail. Here we describe the first remains of juvenile individuals, isolated cervical and dorsal neural arches from Switzerland. These were separated postmortem from their respective centra because of unfused neurocentral sutures. However the specimens share the same neural arch morphology found in adults. Morphometric analysis suggests body lengths of the juvenile individuals that is greater than those of most adult specimens. This supports the hypothesis of developmental plasticity in Plateosaurus engelhardti that previously had been based on histological data only. Alternative hypotheses for explaining the poor correlation between ontogenetic stage and size in this taxon are multiple species or sexual morphs with little morphological variance or time-averaging of individuals from populations differing in body size.

  20. Bone histology of the titanosaur Lirainosaurus astibiae (Dinosauria: Sauropoda) from the Latest Cretaceous of Spain.

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    Company, Julio

    2011-01-01

    The titanosaur Lirainosaurus astibiae is the only sauropod species known from the Late Cretaceous of the Iberian Peninsula. Lirainosaurus did not reach a gigantic body size and is one of the smallest sauropods discovered to date. Histological analysis of Lirainosaurus bones, focused on diaphyseal transverse sections of appendicular elements, reveals that Lirainosaurus did not exhibit the osseous microstructure typical for large sauropods, but is comparable with that of the coeval titanosaurs Alamosaurus sanjuanensis, Ampelosaurus atacis, and Magyarosaurus dacus, and also shares histological traits with other small to medium-sized sauropodomorph dinosaurs. Lirainosaurus limb bones exhibit a laminar fibrolamellar bone microstructure interrupted by growth marks, fully obliterated in adulthood by intense secondary remodeling processes which tend to replace completely the primary cortex. Lirainosaurus attained smaller sizes than typical sauropods reducing the rate of primary periosteal osteogenesis and developing an extensive secondary remodeling well before the adult size was reached. Histological organization of Lirainosaurus long bones is more mature than observed in basal neosauropods at similar ontogenetic stage, documenting a case of peramorphosis by pre-displacement. This heterochronic growth would be a reversal of the accelerated pattern of bone deposition typical for the sauropod lineage.

  1. Histologic Examination of an Assemblage of Psittacosaurus (Dinosauria: Ceratopsia) Juveniles From the Yixian Formation (Liaoning, China).

    Science.gov (United States)

    Bo, Zhao; Hedrick, Brandon P; Chunling, Gao; Tumarkin-Deratzian, Allison R; Fengjiao, Zhang; Caizhi, Shen; Dodson, Peter

    2016-05-01

    Psittacosaurus is one of the most abundant dinosaurs known, which allows for extensive study of its growth and form. Previous studies have evaluated growth trajectories of Psittacosaurus using bone histology. However, we present the first study of Psittacosaurus comparative juvenile histology and describe the histology of Psittacosaurus within its first year of life based on multiple sections taken from an exquisite monospecific assemblage of juveniles from the Yixian Formation in Liaoning, China. Specimens studied had femur lengths ranging from 30 to 36 mm. The five juveniles examined all have similar histologic patterns in the midshaft and epiphyseal regions showing that there is limited plasticity in bone development in juvenile Psittacosaurus and that all of the specimens in the assemblage were likely the same age. The microstructure patterns are compatible with the hypothesis that Psittacosaurus was precocial and that these juveniles were neonates. Based on comparisons with other juvenile ornithischians, juvenile Psittacosaurus had a growth rate similar to Orodromeus, slower than that of Maiasaura, Dysalotosaurus, or hadrosaurs consistent with small body size. Our results support previous studies that demonstrated that the orientation of vascular canals is likely not solely reflective of growth rate, but is also affected by underlying biomechanical, structural processes. The number of studies done on theropod and sauropodomorph histology dwarfs those of ornithischians. More studies of ornithischian histology are necessary in order to better establish phylogenetic trends in microstructure and to learn more about growth in this important clade. © 2016 Wiley Periodicals, Inc.

  2. Bone histology of the titanosaur Lirainosaurus astibiae (Dinosauria: Sauropoda) from the Latest Cretaceous of Spain

    Science.gov (United States)

    Company, Julio

    2011-01-01

    The titanosaur Lirainosaurus astibiae is the only sauropod species known from the Late Cretaceous of the Iberian Peninsula. Lirainosaurus did not reach a gigantic body size and is one of the smallest sauropods discovered to date. Histological analysis of Lirainosaurus bones, focused on diaphyseal transverse sections of appendicular elements, reveals that Lirainosaurus did not exhibit the osseous microstructure typical for large sauropods, but is comparable with that of the coeval titanosaurs Alamosaurus sanjuanensis, Ampelosaurus atacis, and Magyarosaurus dacus, and also shares histological traits with other small to medium-sized sauropodomorph dinosaurs. Lirainosaurus limb bones exhibit a laminar fibrolamellar bone microstructure interrupted by growth marks, fully obliterated in adulthood by intense secondary remodeling processes which tend to replace completely the primary cortex. Lirainosaurus attained smaller sizes than typical sauropods reducing the rate of primary periosteal osteogenesis and developing an extensive secondary remodeling well before the adult size was reached. Histological organization of Lirainosaurus long bones is more mature than observed in basal neosauropods at similar ontogenetic stage, documenting a case of peramorphosis by pre-displacement. This heterochronic growth would be a reversal of the accelerated pattern of bone deposition typical for the sauropod lineage.

  3. A revised cranial description of Massospondylus carinatus Owen (Dinosauria: Sauropodomorpha based on computed tomographic scans and a review of cranial characters for basal Sauropodomorpha

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    Kimberley E.J. Chapelle

    2018-01-01

    Full Text Available Massospondylus carinatus is a basal sauropodomorph dinosaur from the early Jurassic Elliot Formation of South Africa. It is one of the best-represented fossil dinosaur taxa, known from hundreds of specimens including at least 13 complete or nearly complete skulls. Surprisingly, the internal cranial anatomy of M. carinatus has never been described using computed tomography (CT methods. Using CT scans and 3D digital representations, we digitally reconstruct the bones of the facial skeleton, braincase, and palate of a complete, undistorted cranium of M. carinatus (BP/1/5241. We describe the anatomical features of the cranial bones, and compare them to other closely related sauropodomorph taxa such as Plateosaurus erlenbergiensis, Lufengosaurus huenei, Sarahsaurus aurifontanalis and Efraasia minor. We identify a suite of character states of the skull and braincase for M. carinatus that sets it apart from other taxa, but these remain tentative due to the lack of comparative sauropodomorph braincase descriptions in the literature. Furthermore, we hypothesize 27 new cranial characters useful for determining relationships in non-sauropodan Sauropodomorpha, delete five pre-existing characters and revise the scores of several existing cranial characters to make more explicit homology statements. All the characters that we hypothesized or revised are illustrated. Using parsimony as an optimality criterion, we then test the relationships of M. carinatus (using BP/1/5241 as a specimen-level exemplar in our revised phylogenetic data matrix.

  4. First evidence of dinosaurian secondary cartilage in the post-hatching skull of Hypacrosaurus stebingeri (Dinosauria, Ornithischia).

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    Bailleul, Alida M; Hall, Brian K; Horner, John R

    2012-01-01

    Bone and calcified cartilage can be fossilized and preserved for hundreds of millions of years. While primary cartilage is fairly well studied in extant and fossilized organisms, nothing is known about secondary cartilage in fossils. In extant birds, secondary cartilage arises after bone formation during embryonic life at articulations, sutures and muscular attachments in order to accommodate mechanical stress. Considering the phylogenetic inclusion of birds within the Dinosauria, we hypothesized a dinosaurian origin for this "avian" tissue. Therefore, histological thin sectioning was used to investigate secondary chondrogenesis in disarticulated craniofacial elements of several post-hatching specimens of the non-avian dinosaur Hypacrosaurus stebingeri (Ornithischia, Lambeosaurinae). Secondary cartilage was found on three membrane bones directly involved with masticatory function: (1) as nodules on the dorso-caudal face of a surangular; and (2) on the bucco-caudal face of a maxilla; and (3) between teeth as islets in the alveolar processes of a dentary. Secondary chondrogenesis at these sites is consistent with the locations of secondary cartilage in extant birds and with the induction of the cartilage by different mechanical factors - stress generated by the articulation of the quadrate, stress of a ligamentous or muscular insertion, and stress of tooth formation. Thus, our study reveals the first evidence of "avian" secondary cartilage in a non-avian dinosaur. It pushes the origin of this "avian" tissue deep into dinosaurian ancestry, suggesting the creation of the more appropriate term "dinosaurian" secondary cartilage.

  5. Cranial growth and variation in edmontosaurs (Dinosauria: Hadrosauridae: implications for latest Cretaceous megaherbivore diversity in North America.

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    Nicolás E Campione

    Full Text Available The well-sampled Late Cretaceous fossil record of North America remains the only high-resolution dataset for evaluating patterns of dinosaur diversity leading up to the terminal Cretaceous extinction event. Hadrosaurine hadrosaurids (Dinosauria: Ornithopoda closely related to Edmontosaurus are among the most common megaherbivores in latest Campanian and Maastrichtian deposits of western North America. However, interpretations of edmontosaur species richness and biostratigraphy have been in constant flux for almost three decades, although the clade is generally thought to have undergone a radiation in the late Maastrichtian. We address the issue of edmontosaur diversity for the first time using rigorous morphometric analyses of virtually all known complete edmontosaur skulls. Results suggest only two valid species, Edmontosaurus regalis from the late Campanian, and E. annectens from the late Maastrichtian, with previously named taxa, including the controversial Anatotitan copei, erected on hypothesized transitional morphologies associated with ontogenetic size increase and allometric growth. A revision of North American hadrosaurid taxa suggests a decrease in both hadrosaurid diversity and disparity from the early to late Maastrichtian, a pattern likely also present in ceratopsid dinosaurs. A decline in the disparity of dominant megaherbivores in the latest Maastrichtian interval supports the hypothesis that dinosaur diversity decreased immediately preceding the end Cretaceous extinction event.

  6. First evidence of dinosaurian secondary cartilage in the post-hatching skull of Hypacrosaurus stebingeri (Dinosauria, Ornithischia.

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    Alida M Bailleul

    Full Text Available Bone and calcified cartilage can be fossilized and preserved for hundreds of millions of years. While primary cartilage is fairly well studied in extant and fossilized organisms, nothing is known about secondary cartilage in fossils. In extant birds, secondary cartilage arises after bone formation during embryonic life at articulations, sutures and muscular attachments in order to accommodate mechanical stress. Considering the phylogenetic inclusion of birds within the Dinosauria, we hypothesized a dinosaurian origin for this "avian" tissue. Therefore, histological thin sectioning was used to investigate secondary chondrogenesis in disarticulated craniofacial elements of several post-hatching specimens of the non-avian dinosaur Hypacrosaurus stebingeri (Ornithischia, Lambeosaurinae. Secondary cartilage was found on three membrane bones directly involved with masticatory function: (1 as nodules on the dorso-caudal face of a surangular; and (2 on the bucco-caudal face of a maxilla; and (3 between teeth as islets in the alveolar processes of a dentary. Secondary chondrogenesis at these sites is consistent with the locations of secondary cartilage in extant birds and with the induction of the cartilage by different mechanical factors - stress generated by the articulation of the quadrate, stress of a ligamentous or muscular insertion, and stress of tooth formation. Thus, our study reveals the first evidence of "avian" secondary cartilage in a non-avian dinosaur. It pushes the origin of this "avian" tissue deep into dinosaurian ancestry, suggesting the creation of the more appropriate term "dinosaurian" secondary cartilage.

  7. The origin and early evolution of dinosaurs.

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    Langer, Max C; Ezcurra, Martin D; Bittencourt, Jonathas S; Novas, Fernando E

    2010-02-01

    The oldest unequivocal records of Dinosauria were unearthed from Late Triassic rocks (approximately 230 Ma) accumulated over extensional rift basins in southwestern Pangea. The better known of these are Herrerasaurus ischigualastensis, Pisanosaurus mertii, Eoraptor lunensis, and Panphagia protos from the Ischigualasto Formation, Argentina, and Staurikosaurus pricei and Saturnalia tupiniquim from the Santa Maria Formation, Brazil. No uncontroversial dinosaur body fossils are known from older strata, but the Middle Triassic origin of the lineage may be inferred from both the footprint record and its sister-group relation to Ladinian basal dinosauromorphs. These include the typical Marasuchus lilloensis, more basal forms such as Lagerpeton and Dromomeron, as well as silesaurids: a possibly monophyletic group composed of Mid-Late Triassic forms that may represent immediate sister taxa to dinosaurs. The first phylogenetic definition to fit the current understanding of Dinosauria as a node-based taxon solely composed of mutually exclusive Saurischia and Ornithischia was given as "all descendants of the most recent common ancestor of birds and Triceratops". Recent cladistic analyses of early dinosaurs agree that Pisanosaurus mertii is a basal ornithischian; that Herrerasaurus ischigualastensis and Staurikosaurus pricei belong in a monophyletic Herrerasauridae; that herrerasaurids, Eoraptor lunensis, and Guaibasaurus candelariensis are saurischians; that Saurischia includes two main groups, Sauropodomorpha and Theropoda; and that Saturnalia tupiniquim is a basal member of the sauropodomorph lineage. On the contrary, several aspects of basal dinosaur phylogeny remain controversial, including the position of herrerasaurids, E. lunensis, and G. candelariensis as basal theropods or basal saurischians, and the affinity and/or validity of more fragmentary taxa such as Agnosphitys cromhallensis, Alwalkeria maleriensis, Chindesaurus bryansmalli, Saltopus elginensis, and

  8. A revision of Sanpasaurus yaoi Young, 1944 from the Early Jurassic of China, and its relevance to the early evolution of Sauropoda (Dinosauria)

    Science.gov (United States)

    Upchurch, Paul; Mannion, Philip D.; Sullivan, Corwin; Butler, Richard J.

    2016-01-01

    The Early Jurassic of China has long been recognized for its diverse array of sauropodomorph dinosaurs. However, the contribution of this record to our understanding of early sauropod evolution is complicated by a dearth of information on important transitional taxa. We present a revision of the poorly known taxon Sanpasaurus yaoi Young, 1944 from the late Early Jurassic Ziliujing Formation of Sichuan Province, southwest China. Initially described as the remains of an ornithopod ornithischian, we demonstrate that the material catalogued as IVPP V156 is unambiguously referable to Sauropoda. Although represented by multiple individuals of equivocal association, Sanpasaurus is nonetheless diagnosable with respect to an autapomorphic feature of the holotypic dorsal vertebral series. Additional material thought to be collected from the type locality is tentatively referred to Sanpasaurus. If correctly attributed, a second autapomorphy is present in a referred humerus. The presence of a dorsoventrally compressed pedal ungual in Sanpasaurus is of particular interest, with taxa possessing this typically ‘vulcanodontid’ character exhibiting a much broader geographic distribution than previously thought. Furthermore, the association of this trait with other features of Sanpasaurus that are broadly characteristic of basal eusauropods underscores the mosaic nature of the early sauropod–eusauropod transition. Our revision of Sanpasaurus has palaeobiogeographic implications for Early Jurassic sauropods, with evidence that the group maintained a cosmopolitan Pangaean distribution. PMID:27781168

  9. A revision ofSanpasaurus yaoiYoung, 1944 from the Early Jurassic of China, and its relevance to the early evolution of Sauropoda (Dinosauria).

    Science.gov (United States)

    McPhee, Blair W; Upchurch, Paul; Mannion, Philip D; Sullivan, Corwin; Butler, Richard J; Barrett, Paul M

    2016-01-01

    The Early Jurassic of China has long been recognized for its diverse array of sauropodomorph dinosaurs. However, the contribution of this record to our understanding of early sauropod evolution is complicated by a dearth of information on important transitional taxa. We present a revision of the poorly known taxon Sanpasaurus yaoi Young, 1944 from the late Early Jurassic Ziliujing Formation of Sichuan Province, southwest China. Initially described as the remains of an ornithopod ornithischian, we demonstrate that the material catalogued as IVPP V156 is unambiguously referable to Sauropoda. Although represented by multiple individuals of equivocal association, Sanpasaurus is nonetheless diagnosable with respect to an autapomorphic feature of the holotypic dorsal vertebral series. Additional material thought to be collected from the type locality is tentatively referred to Sanpasaurus . If correctly attributed, a second autapomorphy is present in a referred humerus. The presence of a dorsoventrally compressed pedal ungual in Sanpasaurus is of particular interest, with taxa possessing this typically 'vulcanodontid' character exhibiting a much broader geographic distribution than previously thought. Furthermore, the association of this trait with other features of Sanpasaurus that are broadly characteristic of basal eusauropods underscores the mosaic nature of the early sauropod-eusauropod transition. Our revision of Sanpasaurus has palaeobiogeographic implications for Early Jurassic sauropods, with evidence that the group maintained a cosmopolitan Pangaean distribution.

  10. A revision of Sanpasaurus yaoi Young, 1944 from the Early Jurassic of China, and its relevance to the early evolution of Sauropoda (Dinosauria

    Directory of Open Access Journals (Sweden)

    Blair W. McPhee

    2016-10-01

    Full Text Available The Early Jurassic of China has long been recognized for its diverse array of sauropodomorph dinosaurs. However, the contribution of this record to our understanding of early sauropod evolution is complicated by a dearth of information on important transitional taxa. We present a revision of the poorly known taxon Sanpasaurus yaoi Young, 1944 from the late Early Jurassic Ziliujing Formation of Sichuan Province, southwest China. Initially described as the remains of an ornithopod ornithischian, we demonstrate that the material catalogued as IVPP V156 is unambiguously referable to Sauropoda. Although represented by multiple individuals of equivocal association, Sanpasaurus is nonetheless diagnosable with respect to an autapomorphic feature of the holotypic dorsal vertebral series. Additional material thought to be collected from the type locality is tentatively referred to Sanpasaurus. If correctly attributed, a second autapomorphy is present in a referred humerus. The presence of a dorsoventrally compressed pedal ungual in Sanpasaurus is of particular interest, with taxa possessing this typically ‘vulcanodontid’ character exhibiting a much broader geographic distribution than previously thought. Furthermore, the association of this trait with other features of Sanpasaurus that are broadly characteristic of basal eusauropods underscores the mosaic nature of the early sauropod–eusauropod transition. Our revision of Sanpasaurus has palaeobiogeographic implications for Early Jurassic sauropods, with evidence that the group maintained a cosmopolitan Pangaean distribution.

  11. A new hypothesis of dinosaur relationships and early dinosaur evolution.

    Science.gov (United States)

    Baron, Matthew G; Norman, David B; Barrett, Paul M

    2017-03-22

    For 130 years, dinosaurs have been divided into two distinct clades-Ornithischia and Saurischia. Here we present a hypothesis for the phylogenetic relationships of the major dinosaurian groups that challenges the current consensus concerning early dinosaur evolution and highlights problematic aspects of current cladistic definitions. Our study has found a sister-group relationship between Ornithischia and Theropoda (united in the new clade Ornithoscelida), with Sauropodomorpha and Herrerasauridae (as the redefined Saurischia) forming its monophyletic outgroup. This new tree topology requires redefinition and rediagnosis of Dinosauria and the subsidiary dinosaurian clades. In addition, it forces re-evaluations of early dinosaur cladogenesis and character evolution, suggests that hypercarnivory was acquired independently in herrerasaurids and theropods, and offers an explanation for many of the anatomical features previously regarded as notable convergences between theropods and early ornithischians.

  12. Jaw mechanics in basal ceratopsia (Ornithischia, Dinosauria).

    Science.gov (United States)

    Tanoue, Kyo; Grandstaff, Barbara S; You, Hai-Lu; Dodson, Peter

    2009-09-01

    Ceratopsian dinosaurs were a dominant group of herbivores in Cretaceous terrestrial ecosystems. We hypothesize that an understanding of the feeding system will provide important insight into the evolutionary success of these animals. The mandibular mechanics of eight genera of basal ceratopsians was examined to understand the variability in shape of the jaws and the early evolution of the masticatory system in Ceratopsia. Data were collected on lever arms, cranial angles and tooth row lengths. The results indicate that psittacosaurids had higher leverage at the beak and in the rostral part of the tooth row than basal neoceratopsians, but lower leverage in the caudal part of the tooth row. Although the vertebrate mandible is generally considered as a third-class lever, that of basal neoceratopsians acted as a second-class lever at the caudal part of the tooth row, as is also true in ceratopsids. When total input force from the mandibular adductor muscles on both sides of the skull is considered, the largest bite force in basal ceratopsian tooth rows was exerted in the caudal part of the tooth row at the caudal extremity of the zone with near-maximum input force. Medially positioned teeth generate higher leverage than laterally positioned teeth. The largest bite force in all basal ceratopsians is smaller than the maximum input force, a limit imposed by the morphology of the basal ceratopsian masticatory system. In ceratopsids, caudal extension of the tooth row resulted in a much larger bite force, even exceeding the maximum input force. (c) 2009 Wiley-Liss, Inc.

  13. Metabolism of dinosaurs as determined from their growth.

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    Lee, Scott A

    2015-09-01

    A model based on cellular properties is used to analyze the mass growth curves of 20 dinosaurs. This analysis yields the first measurement of the average cellular metabolism of dinosaurs. The organismal metabolism is also determined. The cellular metabolism of dinosaurs is found to decrease with mass at a slower rate than is observed in extant animals. The organismal metabolism increases with the mass of the dinosaur. These results come from both the Saurischia and Ornithischia branches of Dinosauria, suggesting that the observed metabolic features were common to all dinosaurs. The results from dinosaurs are compared to data from extant placental and marsupial mammals, a monotreme, and altricial and precocial birds, reptiles, and fish. Dinosaurs had cellular and organismal metabolisms in the range observed in extant mesotherms.

  14. Sauropod dinosaurs evolved moderately sized genomes unrelated to body size.

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    Organ, Chris L; Brusatte, Stephen L; Stein, Koen

    2009-12-22

    Sauropodomorph dinosaurs include the largest land animals to have ever lived, some reaching up to 10 times the mass of an African elephant. Despite their status defining the upper range for body size in land animals, it remains unknown whether sauropodomorphs evolved larger-sized genomes than non-avian theropods, their sister taxon, or whether a relationship exists between genome size and body size in dinosaurs, two questions critical for understanding broad patterns of genome evolution in dinosaurs. Here we report inferences of genome size for 10 sauropodomorph taxa. The estimates are derived from a Bayesian phylogenetic generalized least squares approach that generates posterior distributions of regression models relating genome size to osteocyte lacunae volume in extant tetrapods. We estimate that the average genome size of sauropodomorphs was 2.02 pg (range of species means: 1.77-2.21 pg), a value in the upper range of extant birds (mean = 1.42 pg, range: 0.97-2.16 pg) and near the average for extant non-avian reptiles (mean = 2.24 pg, range: 1.05-5.44 pg). The results suggest that the variation in size and architecture of genomes in extinct dinosaurs was lower than the variation found in mammals. A substantial difference in genome size separates the two major clades within dinosaurs, Ornithischia (large genomes) and Saurischia (moderate to small genomes). We find no relationship between body size and estimated genome size in extinct dinosaurs, which suggests that neutral forces did not dominate the evolution of genome size in this group.

  15. The Venice specimen of Ouranosaurus nigeriensis (Dinosauria, Ornithopoda

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    Filippo Bertozzo

    2017-06-01

    Full Text Available Ouranosaurus nigeriensis is an iconic African dinosaur taxon that has been described on the basis of two nearly complete skeletons from the Lower Cretaceous Gadoufaoua locality of the Ténéré desert in Niger. The entire holotype and a few bones attributed to the paratype formed the basis of the original description by Taquet (1976. A mounted skeleton that appears to correspond to O. nigeriensis has been on public display since 1975, exhibited at the Natural History Museum of Venice. It was never explicitly reported whether the Venice specimen represents a paratype and therefore, the second nearly complete skeleton reported in literature or a third unreported skeleton. The purpose of this paper is to disentangle the complex history of the various skeletal remains that have been attributed to Ouranosaurus nigeriensis (aided by an unpublished field map of the paratype and to describe in detail the osteology of the Venice skeleton. The latter includes the paratype material (found in 1970 and collected in 1972, with the exception of the left femur, the right coracoid and one manus ungual phalanx I, which were replaced with plaster copies, and (possibly other manus phalanges. Some other elements (e.g., the first two chevrons, the right femur, the right tibia, two dorsal vertebrae and some pelvic bones were likely added from other individual/s. The vertebral column of the paratype was articulated and provides a better reference for the vertebral count of this taxon than the holotype. Several anatomical differences are observed between the holotype and the Venice specimen. Most of them can be ascribed to intraspecific variability (individual or ontogenetic, but some are probably caused by mistakes in the preparation or assemblage of the skeletal elements in both specimens. The body length of the Venice skeleton is about 90% the linear size of the holotype. Osteohistological analysis (the first for this taxon of some long bones, a rib and a dorsal neural spine reveals that the Venice specimen is a sub-adult; this conclusion is supported by somatic evidence of immaturity. The dorsal ‘sail’ formed by the elongated neural spines of the dorsal, sacral and proximal caudal vertebrae characterizes this taxon among ornithopods; a display role is considered to be the most probable function for this bizarre structure. Compared to the mid-1970s, new information from the Venice specimen and many iguanodontian taxa known today allowed for an improved diagnosis of O. nigeriensis.

  16. Reconsidering the Avian Nature of the Oviraptorosaur Brain (Dinosauria: Theropoda.

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    Amy M Balanoff

    Full Text Available The high degree of encephalization characterizing modern birds is the product of a long evolutionary history, our understanding of which is still largely in its infancy. Here we provide a redescription of the endocranial space of the oviraptorosaurian dinosaur Conchoraptor gracilis with the goal of assessing the hypothesis that it shares uniquely derived endocranial characters with crown-group avians. The existence of such features has implications for the transformational history of avian neuroanatomy and suggests that the oviraptorosaur radiation is a product of the immediate stem lineage of birds-after the divergence of Archaeopteryx lithographica. Results derived from an expanded comparative sample indicate that the strong endocranial similarity between Conchoraptor and modern birds largely reflects shared conservation of plesiomorphic features. The few characters that are maintained as being uniquely expressed in these two taxa are more likely products of convergence than homology but still indicate that the oviraptorosaur endocranial cavity has much to teach us about the complex history of avian brain evolution.

  17. Caudal Pneumaticity and Pneumatic Hiatuses in the Sauropod Dinosaurs Giraffatitan and Apatosaurus

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    Wedel, Mathew J.; Taylor, Michael P.

    2013-01-01

    Skeletal pneumaticity is found in the presacral vertebrae of most sauropod dinosaurs, but pneumaticity is much less common in the vertebrae of the tail. We describe previously unrecognized pneumatic fossae in the mid-caudal vertebrae of specimens of Giraffatitan and Apatosaurus. In both taxa, the most distal pneumatic vertebrae are separated from other pneumatic vertebrae by sequences of three to seven apneumatic vertebrae. Caudal pneumaticity is not prominent in most individuals of either of these taxa, and its unpredictable development means that it may be more widespread than previously recognised within Sauropoda and elsewhere in Saurischia. The erratic patterns of caudal pneumatization in Giraffatitan and Apatosaurus, including the pneumatic hiatuses, show that pneumatic diverticula were more broadly distributed in the bodies of the living animals than are their traces in the skeleton. Together with recently published evidence of cryptic diverticula—those that leave few or no skeletal traces—in basal sauropodomorphs and in pterosaurs, this is further evidence that pneumatic diverticula were widespread in ornithodirans, both across phylogeny and throughout anatomy. PMID:24205162

  18. Caudal pneumaticity and pneumatic hiatuses in the sauropod dinosaurs Giraffatitan and Apatosaurus.

    Science.gov (United States)

    Wedel, Mathew J; Taylor, Michael P

    2013-01-01

    Skeletal pneumaticity is found in the presacral vertebrae of most sauropod dinosaurs, but pneumaticity is much less common in the vertebrae of the tail. We describe previously unrecognized pneumatic fossae in the mid-caudal vertebrae of specimens of Giraffatitan and Apatosaurus. In both taxa, the most distal pneumatic vertebrae are separated from other pneumatic vertebrae by sequences of three to seven apneumatic vertebrae. Caudal pneumaticity is not prominent in most individuals of either of these taxa, and its unpredictable development means that it may be more widespread than previously recognised within Sauropoda and elsewhere in Saurischia. The erratic patterns of caudal pneumatization in Giraffatitan and Apatosaurus, including the pneumatic hiatuses, show that pneumatic diverticula were more broadly distributed in the bodies of the living animals than are their traces in the skeleton. Together with recently published evidence of cryptic diverticula--those that leave few or no skeletal traces--in basal sauropodomorphs and in pterosaurs, this is further evidence that pneumatic diverticula were widespread in ornithodirans, both across phylogeny and throughout anatomy.

  19. Forelimb muscle and joint actions in Archosauria: insights from Crocodylus johnstoni (Pseudosuchia) and Mussaurus patagonicus (Sauropodomorpha)

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    Allen, Vivian

    2017-01-01

    Many of the major locomotor transitions during the evolution of Archosauria, the lineage including crocodiles and birds as well as extinct Dinosauria, were shifts from quadrupedalism to bipedalism (and vice versa). Those occurred within a continuum between more sprawling and erect modes of locomotion and involved drastic changes of limb anatomy and function in several lineages, including sauropodomorph dinosaurs. We present biomechanical computer models of two locomotor extremes within Archosauria in an analysis of joint ranges of motion and the moment arms of the major forelimb muscles in order to quantify biomechanical differences between more sprawling, pseudosuchian (represented the crocodile Crocodylus johnstoni) and more erect, dinosaurian (represented by the sauropodomorph Mussaurus patagonicus) modes of forelimb function. We compare these two locomotor extremes in terms of the reconstructed musculoskeletal anatomy, ranges of motion of the forelimb joints and the moment arm patterns of muscles across those ranges of joint motion. We reconstructed the three-dimensional paths of 30 muscles acting around the shoulder, elbow and wrist joints. We explicitly evaluate how forelimb joint mobility and muscle actions may have changed with postural and anatomical alterations from basal archosaurs to early sauropodomorphs. We thus evaluate in which ways forelimb posture was correlated with muscle leverage, and how such differences fit into a broader evolutionary context (i.e. transition from sprawling quadrupedalism to erect bipedalism and then shifting to graviportal quadrupedalism). Our analysis reveals major differences of muscle actions between the more sprawling and erect models at the shoulder joint. These differences are related not only to the articular surfaces but also to the orientation of the scapula, in which extension/flexion movements in Crocodylus (e.g. protraction of the humerus) correspond to elevation/depression in Mussaurus. Muscle action is highly

  20. Forelimb muscle and joint actions in Archosauria: insights from Crocodylus johnstoni (Pseudosuchia) and Mussaurus patagonicus (Sauropodomorpha).

    Science.gov (United States)

    Otero, Alejandro; Allen, Vivian; Pol, Diego; Hutchinson, John R

    2017-01-01

    Many of the major locomotor transitions during the evolution of Archosauria, the lineage including crocodiles and birds as well as extinct Dinosauria, were shifts from quadrupedalism to bipedalism (and vice versa). Those occurred within a continuum between more sprawling and erect modes of locomotion and involved drastic changes of limb anatomy and function in several lineages, including sauropodomorph dinosaurs. We present biomechanical computer models of two locomotor extremes within Archosauria in an analysis of joint ranges of motion and the moment arms of the major forelimb muscles in order to quantify biomechanical differences between more sprawling, pseudosuchian (represented the crocodile Crocodylus johnstoni) and more erect, dinosaurian (represented by the sauropodomorph Mussaurus patagonicus) modes of forelimb function. We compare these two locomotor extremes in terms of the reconstructed musculoskeletal anatomy, ranges of motion of the forelimb joints and the moment arm patterns of muscles across those ranges of joint motion. We reconstructed the three-dimensional paths of 30 muscles acting around the shoulder, elbow and wrist joints. We explicitly evaluate how forelimb joint mobility and muscle actions may have changed with postural and anatomical alterations from basal archosaurs to early sauropodomorphs. We thus evaluate in which ways forelimb posture was correlated with muscle leverage, and how such differences fit into a broader evolutionary context (i.e. transition from sprawling quadrupedalism to erect bipedalism and then shifting to graviportal quadrupedalism). Our analysis reveals major differences of muscle actions between the more sprawling and erect models at the shoulder joint. These differences are related not only to the articular surfaces but also to the orientation of the scapula, in which extension/flexion movements in Crocodylus (e.g. protraction of the humerus) correspond to elevation/depression in Mussaurus. Muscle action is highly

  1. Forelimb muscle and joint actions in Archosauria: insights from Crocodylus johnstoni (Pseudosuchia and Mussaurus patagonicus (Sauropodomorpha

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    Alejandro Otero

    2017-11-01

    Full Text Available Many of the major locomotor transitions during the evolution of Archosauria, the lineage including crocodiles and birds as well as extinct Dinosauria, were shifts from quadrupedalism to bipedalism (and vice versa. Those occurred within a continuum between more sprawling and erect modes of locomotion and involved drastic changes of limb anatomy and function in several lineages, including sauropodomorph dinosaurs. We present biomechanical computer models of two locomotor extremes within Archosauria in an analysis of joint ranges of motion and the moment arms of the major forelimb muscles in order to quantify biomechanical differences between more sprawling, pseudosuchian (represented the crocodile Crocodylus johnstoni and more erect, dinosaurian (represented by the sauropodomorph Mussaurus patagonicus modes of forelimb function. We compare these two locomotor extremes in terms of the reconstructed musculoskeletal anatomy, ranges of motion of the forelimb joints and the moment arm patterns of muscles across those ranges of joint motion. We reconstructed the three-dimensional paths of 30 muscles acting around the shoulder, elbow and wrist joints. We explicitly evaluate how forelimb joint mobility and muscle actions may have changed with postural and anatomical alterations from basal archosaurs to early sauropodomorphs. We thus evaluate in which ways forelimb posture was correlated with muscle leverage, and how such differences fit into a broader evolutionary context (i.e. transition from sprawling quadrupedalism to erect bipedalism and then shifting to graviportal quadrupedalism. Our analysis reveals major differences of muscle actions between the more sprawling and erect models at the shoulder joint. These differences are related not only to the articular surfaces but also to the orientation of the scapula, in which extension/flexion movements in Crocodylus (e.g. protraction of the humerus correspond to elevation/depression in Mussaurus. Muscle

  2. Pelvis of gargoyleosaurus (Dinosauria: Ankylosauria and the origin and evolution of the ankylosaur pelvis.

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    Kenneth Carpenter

    Full Text Available Discovery of a pelvis attributed to the Late Jurassic armor-plated dinosaur Gargoyleosaurus sheds new light on the origin of the peculiar non-vertical, broad, flaring pelvis of ankylosaurs. It further substantiates separation of the two ankylosaurs from the Morrison Formation of the western United States, Gargoyleosaurus and Mymoorapelta. Although horizontally oriented and lacking the medial curve of the preacetabular process seen in Mymoorapelta, the new ilium shows little of the lateral flaring seen in the pelvis of Cretaceous ankylosaurs. Comparison with the basal thyreophoran Scelidosaurus demonstrates that the ilium in ankylosaurs did not develop entirely by lateral rotation as is commonly believed. Rather, the preacetabular process rotated medially and ventrally and the postacetabular process rotated in opposition, i.e., lateral and ventrally. Thus, the dorsal surfaces of the preacetabular and postacetabular processes are not homologous. In contrast, a series of juvenile Stegosaurus ilia show that the postacetabular process rotated dorsally ontogenetically. Thus, the pelvis of the two major types of Thyreophora most likely developed independently. Examination of other ornithischians show that a non-vertical ilium had developed independently in several different lineages, including ceratopsids, pachycephalosaurs, and iguanodonts. Therefore, a separate origin for the non-vertical ilium in stegosaurs and ankylosaurs does have precedent.

  3. A Centrosaurine (Dinosauria: Ceratopsia from the Aguja Formation (Late Campanian of Northern Coahuila, Mexico.

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    Héctor E Rivera-Sylva

    Full Text Available While centrosaurines and ceratopsids in general are abundant in the Late Campanian of northern Laramidia, they are much less commonly found in southern Laramidia. This has supported hypotheses of dinosaur provinciality and endemism in the Late Cretaceous with the delineation of at least two separate faunal zones, north and south Laramidia. There have been 12 genera of centrosaurines recognized from northern Laramidia while two genera, Diabloceratops and Nasutoceratops, have been named from southern Laramidia. We present an osteological description and taphonomic outline for a new centrosaurine ceratopsid from the Aguja Formation of northern Coahuila, Mexico that is not currently diagnosable to the generic level, but likely represents a new taxon. Further, we have included three-dimensional surface scans of all material attributed to this animal. Considering the large number of centrosaurines from northern Laramidia, it is likely that cladistic analyses are biased towards this faunal zone. New findings of southern centrosaurines are needed to correct this bias. This discovery expands the range of centrosaurines south to Coahuila, Mexico and adds new information to better characterize the morphology and taxonomy of centrosaurines from southern Laramidia and their evolution in comparison to their northern counterparts.

  4. A Centrosaurine (Dinosauria: Ceratopsia) from the Aguja Formation (Late Campanian) of Northern Coahuila, Mexico

    OpenAIRE

    Rivera-Sylva, H?ctor E.; Hedrick, Brandon P.; Dodson, Peter

    2016-01-01

    While centrosaurines and ceratopsids in general are abundant in the Late Campanian of northern Laramidia, they are much less commonly found in southern Laramidia. This has supported hypotheses of dinosaur provinciality and endemism in the Late Cretaceous with the delineation of at least two separate faunal zones, north and south Laramidia. There have been 12 genera of centrosaurines recognized from northern Laramidia while two genera, Diabloceratops and Nasutoceratops, have been named from so...

  5. An Injured Psittacosaurus (Dinosauria: Ceratopsia) From the Yixian Formation (Liaoning, China): Implications for Psittacosaurus Biology.

    Science.gov (United States)

    Hedrick, B P; Gao, C; Tumarkin-Deratzian, A R; Shen, C; Holloway, J L; Zhang, F; Hankenson, K D; Liu, S; Anné, J; Dodson, P

    2016-07-01

    We describe a Psittacosaurus specimen from the Lujiatun beds of the Yixian Formation in Liaoning, China with an abnormality on its left fibula. Although a large number of Psittacosaurus specimens are known, only a single example of a pathologic Psittacosaurus has been previously noted. The specific pathology in the current specimen is believed to be a healed fibular fracture as assessed through a combination of gross morphology, microcomputed tomography (microCT), and histology data. The fracture can be identified using microCT, but the degree of remodeling and the stage of fracture repair are best determined histologically. The fracture callus is made up of radially oriented spokes of woven bone in a cartilage matrix and the original cortical bone prior to the fracture has been largely eroded. A transverse histologic section taken at the level of the fracture shows the displacement of the proximal and distal parts of the fibula. The Psittacosaurus appears to have survived the break considering the deposition of circumferential non-pathologic bone at the periosteal surface outside of the callus. The combination of gross morphological description, microCT data, and histologic data allowed for a full diagnosis of the abnormality. While some previous authors have preferred gross morphological description above other methods for assessing paleopathologies, it is evident based on this specimen that an amalgam of techniques provides greater clarity to paleopathology diagnoses. Although this Psittacosaurus lived in an environment with many predators, it was able to survive with a fracture on its hindlimb, which undoubtedly would have impacted its locomotion. Anat Rec, 299:897-906, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  6. A Centrosaurine (Dinosauria: Ceratopsia) from the Aguja Formation (Late Campanian) of Northern Coahuila, Mexico.

    Science.gov (United States)

    Rivera-Sylva, Héctor E; Hedrick, Brandon P; Dodson, Peter

    2016-01-01

    While centrosaurines and ceratopsids in general are abundant in the Late Campanian of northern Laramidia, they are much less commonly found in southern Laramidia. This has supported hypotheses of dinosaur provinciality and endemism in the Late Cretaceous with the delineation of at least two separate faunal zones, north and south Laramidia. There have been 12 genera of centrosaurines recognized from northern Laramidia while two genera, Diabloceratops and Nasutoceratops, have been named from southern Laramidia. We present an osteological description and taphonomic outline for a new centrosaurine ceratopsid from the Aguja Formation of northern Coahuila, Mexico that is not currently diagnosable to the generic level, but likely represents a new taxon. Further, we have included three-dimensional surface scans of all material attributed to this animal. Considering the large number of centrosaurines from northern Laramidia, it is likely that cladistic analyses are biased towards this faunal zone. New findings of southern centrosaurines are needed to correct this bias. This discovery expands the range of centrosaurines south to Coahuila, Mexico and adds new information to better characterize the morphology and taxonomy of centrosaurines from southern Laramidia and their evolution in comparison to their northern counterparts.

  7. The first specimen of Camarasaurus (Dinosauria: Sauropoda from Montana: The northernmost occurrence of the genus.

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    D Cary Woodruff

    Full Text Available A partial skeleton from the Little Snowy Mountains of central Montana is the first referable specimen of the Morrison Formation macronarian sauropod Camarasaurus. This specimen also represents the northernmost occurrence of a sauropod in the Morrison. Histological study indicates that, although the specimen is relatively small statured, it is skeletally mature; this further emphasizes that size is not a undeviating proxy to maturity in dinosaurs, and that morphologies associated with an individual's age and stature may be more nebulous in sauropods.

  8. A New Megaraptoran Dinosaur (Dinosauria, Theropoda, Megaraptoridae from the Late Cretaceous of Patagonia.

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    Rodolfo A Coria

    Full Text Available A skeleton discovered in the Upper Cretaceous Sierra Barrosa Formation (Turonian-Coniacian of Neuquén Province, Argentina represents a new species of theropod dinosaur related to the long snouted, highly pneumatized Megaraptoridae. The holotype specimen of Murusraptor barrosaensis n.gen et n.sp. (MCF-PVPH-411 includes much of the skull, axial skeleton, pelvis and tibia. Murusraptor is unique in having several diagnostic features that include anterodorsal process of lacrimal longer than height of preorbital process, and a thick, shelf-like thickening on the lateral surface of surangular ventral to the groove between the anterior surangular foramen and the insert for the uppermost intramandibular process of the dentary. Other characteristic features of Murusraptor barrosaensis n.gen. et n. sp.include a large mandibular fenestra, distal ends of caudal neural spines laterally thickened into lateral knob-like processes, short ischia distally flattened and slightly expanded dorsoventrally. Murusraptor belongs to a Patagonian radiation of megaraptorids together with Aerosteon, Megaraptor and Orkoraptor. In spite being immature, it is a larger but more gracile animal than existing specimens of Megaraptor, and is comparable in size with Aerosteon and Orkoraptor. The controversial phylogeny of the Megaraptoridae as members of the Allosauroidea or a clade of Coelurosauria is considered analyzing two alternative data sets.

  9. Osteology of the basal hadrosauroid Eolambia caroljonesa (Dinosauria: Ornithopoda from the Cedar Mountain Formation of Utah.

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    Andrew T McDonald

    Full Text Available BACKGROUND: Eolambia caroljonesa is known from copious remains from the lower Cenomanian Mussentuchit Member of the Cedar Mountain Formation in eastern Utah; however, the taxon has been only briefly described. Thus, we present herein a complete osteological description of Eolambia. METHODOLOGY/PRINCIPAL FINDINGS: The description of Eolambia presented here is based upon the holotype partial skeleton (CEUM 9758, paratype partial skull (CEUM 5212, and abundant disarticulated elements from two bonebeds that contain juvenile individuals. These remains allow the skeletal anatomy of Eolambia to be documented almost fully and a revised diagnosis to be proposed. CONCLUSIONS/SIGNIFICANCE: The description provided here facilitates comparisons between Eolambia and other iguanodontians and allows Eolambia to be coded for additional characters in phylogenetic analyses. The close affinity between Eolambia and Probactrosaurus gobiensis from the Early Cretaceous of China supports previous hypotheses of faunal interchange between Asia and North America in the early Late Cretaceous.

  10. Osteology of the Basal Hadrosauroid Eolambia caroljonesa (Dinosauria: Ornithopoda) from the Cedar Mountain Formation of Utah

    OpenAIRE

    McDonald, Andrew T.; John Bird; Kirkland, James I.; Peter Dodson

    2012-01-01

    BACKGROUND: Eolambia caroljonesa is known from copious remains from the lower Cenomanian Mussentuchit Member of the Cedar Mountain Formation in eastern Utah; however, the taxon has been only briefly described. Thus, we present herein a complete osteological description of Eolambia. METHODOLOGY/PRINCIPAL FINDINGS: The description of Eolambia presented here is based upon the holotype partial skeleton (CEUM 9758), paratype partial skull (CEUM 5212), and abundant disarticulated elements from two ...

  11. Osteology of the Basal Hadrosauroid Eolambia caroljonesa (Dinosauria: Ornithopoda) from the Cedar Mountain Formation of Utah

    Science.gov (United States)

    McDonald, Andrew T.; Bird, John; Kirkland, James I.; Dodson, Peter

    2012-01-01

    Background Eolambia caroljonesa is known from copious remains from the lower Cenomanian Mussentuchit Member of the Cedar Mountain Formation in eastern Utah; however, the taxon has been only briefly described. Thus, we present herein a complete osteological description of Eolambia. Methodology/Principal Findings The description of Eolambia presented here is based upon the holotype partial skeleton (CEUM 9758), paratype partial skull (CEUM 5212), and abundant disarticulated elements from two bonebeds that contain juvenile individuals. These remains allow the skeletal anatomy of Eolambia to be documented almost fully and a revised diagnosis to be proposed. Conclusions/Significance The description provided here facilitates comparisons between Eolambia and other iguanodontians and allows Eolambia to be coded for additional characters in phylogenetic analyses. The close affinity between Eolambia and Probactrosaurus gobiensis from the Early Cretaceous of China supports previous hypotheses of faunal interchange between Asia and North America in the early Late Cretaceous. PMID:23077495

  12. A large abelisaurid (Dinosauria, Theropoda) from Morocco and comments on the Cenomanian theropods from North Africa.

    Science.gov (United States)

    Chiarenza, Alfio Alessandro; Cau, Andrea

    2016-01-01

    We describe the partially preserved femur of a large-bodied theropod dinosaur from the Cenomanian "Kem Kem Compound Assemblage" (KKCA) of Morocco. The fossil is housed in the Museo Geologico e Paleontologico "Gaetano Giorgio Gemmellaro" in Palermo (Italy). The specimen is compared with the theropod fossil record from the KKCA and coeval assemblages from North Africa. The combination of a distally reclined head, a not prominent trochanteric shelf, distally placed lesser trochanter of stout, alariform shape, a stocky shaft with the fourth trochanter placed proximally, and rugose muscular insertion areas in the specimen distinguishes it from Carcharodontosaurus, Deltadromeus and Spinosaurus and supports referral to an abelisaurid. The estimated body size for the individual from which this femur was derived is comparable to Carnotaurus and Ekrixinatosaurus (up to 9 meters in length and 2 tons in body mass). This find confirms that abelisaurids had reached their largest body size in the "middle Cretaceous," and that large abelisaurids coexisted with other giant theropods in Africa. We review the taxonomic status of the theropods from the Cenomanian of North Africa, and provisionally restrict the Linnean binomina Carcharodontosaurus iguidensis and Spinosaurus aegyptiacus to the type specimens. Based on comparisons among the theropod records from the Aptian-Cenomanian of South America and Africa, a partial explanation for the so-called "Stromer's riddle" (namely, the coexistence of many large predatory dinosaurs in the "middle Cretaceous" record from North Africa) is offered in term of taphonomic artifacts among lineage records that were ecologically and environmentally non-overlapping. Although morphofunctional and stratigraphic evidence supports an ecological segregation between spinosaurids and the other lineages, the co-occurrence of abelisaurids and carcharodontosaurids, two groups showing several craniodental convergences that suggest direct resource competition, remains to be explained.

  13. Perinatal Specimens of Saurolophus angustirostris (Dinosauria: Hadrosauridae, from the Upper Cretaceous of Mongolia.

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    Leonard Dewaele

    Full Text Available The Late Cretaceous Nemegt Formation, Gobi Desert, Mongolia has already yielded abundant and complete skeletons of the hadrosaur Saurolophus angustirostris, from half-grown to adult individuals.Herein we describe perinatal specimens of Saurolophus angustirostris, associated with fragmentary eggshell fragments. The skull length of these babies is around 5% that of the largest known S. angustirostris specimens, so these specimens document the earliest development stages of this giant hadrosaur and bridge a large hiatus in our knowledge of the ontogeny of S. angustirostris.The studied specimens are likely part of a nest originally located on a riverbank point bar. The perinatal specimens were buried by sediment carried by the river current presumably during the wet summer season. Perinatal bones already displayed diagnostic characters for Saurolophus angustirostris, including premaxillae with a strongly reflected oral margin and upturned premaxillary body in lateral aspect. The absence of a supracranial crest and unfused halves of the cervical neural arches characterize the earliest stages in the ontogeny of S. angustirostris. The eggshell fragments associated with the perinatal individuals can be referred to the Spheroolithus oogenus and closely resemble those found in older formations (e.g. Barun Goyot Fm in Mongolia or associated with more basal hadrosauroids (Bactrosaurus-Gilmoreosaurus in the Iren Dabasu Fm, Inner Mongolia, China. This observation suggests that the egg microstructure was similar in basal hadrosauroids and more advanced saurolophines.One of the authors (FE is employed by the commercial organization Eldonia. Eldonia provided support in the form of a salary for FE, but did not have any additional role or influence in the study design, data collection and analysis, decision to publish, or preparation of the manuscript and it does not alter the authors' adherence to all the PLoS ONE policies on sharing data and materials.

  14. Posture and mechanics of the forelimbs of Brachiosaurus brancai (Dinosauria: Sauropoda

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    A. Christian

    1999-01-01

    Full Text Available The posture and mechanics of the forelimbs of Brachiosaurus brancai were analysed with the help of biomechanical models. Peak forces in the joints due to acceleration of the fraction of body weight carried on the shoulder joints are critical in models with completely straight, column-like limbs and a rigid shoulder girdle. During fast walking, either the forelimbs were flexed at the elbows during the middle of the support phase or the apparently rigid shoulder girdle allowed movements of the shoulder joints relative to the trunk. The overall construction of Brachiosaurus was related to an extreme task, browsing high above the ground. Consequently, versatility was very restricted. Die Stellung und die Mechanik der Vorderbeine von Brachiosaurus brancai wurden mit Hilfe von biomechanischen Modellen untersucht. Kraftspitzen aufgrund von Beschleunigungen des von den Schultern getragenen Anteils der Körpermasse erscheinen in Modellen mit völlig geraden, säulenförmigen Vorderbeinen und einem unbeweglichen Schultergürtel problematisch. Während des schnellen Gehens waren entweder die Vorderbeine in der Mitte der Stützphase in den Ellenbogengelenken gebeugt oder der scheinbar rigide Schultergürtel erlaubte Bewegungen der Schultergelenke relativ zum Brustkorb. Die Gesamtkonstruktion von Brachiosaurus war auf die Ausübung einer extremen Tätigkeit, die Nahrungsaufnahme in großer Höhe, ausgerichtet. Die Konsequenz war eine geringe Vielseitigkeit. doi:10.1002/mmng.1999.4860020103

  15. Pelvis of gargoyleosaurus (Dinosauria: Ankylosauria) and the origin and evolution of the ankylosaur pelvis.

    Science.gov (United States)

    Carpenter, Kenneth; DiCroce, Tony; Kinneer, Billy; Simon, Robert

    2013-01-01

    Discovery of a pelvis attributed to the Late Jurassic armor-plated dinosaur Gargoyleosaurus sheds new light on the origin of the peculiar non-vertical, broad, flaring pelvis of ankylosaurs. It further substantiates separation of the two ankylosaurs from the Morrison Formation of the western United States, Gargoyleosaurus and Mymoorapelta. Although horizontally oriented and lacking the medial curve of the preacetabular process seen in Mymoorapelta, the new ilium shows little of the lateral flaring seen in the pelvis of Cretaceous ankylosaurs. Comparison with the basal thyreophoran Scelidosaurus demonstrates that the ilium in ankylosaurs did not develop entirely by lateral rotation as is commonly believed. Rather, the preacetabular process rotated medially and ventrally and the postacetabular process rotated in opposition, i.e., lateral and ventrally. Thus, the dorsal surfaces of the preacetabular and postacetabular processes are not homologous. In contrast, a series of juvenile Stegosaurus ilia show that the postacetabular process rotated dorsally ontogenetically. Thus, the pelvis of the two major types of Thyreophora most likely developed independently. Examination of other ornithischians show that a non-vertical ilium had developed independently in several different lineages, including ceratopsids, pachycephalosaurs, and iguanodonts. Therefore, a separate origin for the non-vertical ilium in stegosaurs and ankylosaurs does have precedent.

  16. A Centrosaurine (Dinosauria: Ceratopsia) from the Aguja Formation (Late Campanian) of Northern Coahuila, Mexico

    National Research Council Canada - National Science Library

    Rivera-Sylva, Héctor E; Hedrick, Brandon P; Dodson, Peter

    2016-01-01

    .... We present an osteological description and taphonomic outline for a new centrosaurine ceratopsid from the Aguja Formation of northern Coahuila, Mexico that is not currently diagnosable to the generic...

  17. New insights into the lifestyle of Allosaurus (Dinosauria: Theropoda based on another specimen with multiple pathologies

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    Christian Foth

    2015-05-01

    Full Text Available Adult large-bodied theropods are often found with numerous pathologies. A large, almost complete, probably adult Allosaurus specimen from the Howe Stephens Quarry, Morrison Formation (Late Kimmeridgian–Early Tithonian, Wyoming, exhibits multiple pathologies. Pathologic bones include the left dentary, two cervical vertebrae, one cervical and several dorsal ribs, the left scapula, the left humerus, the right ischium, and two left pedal phalanges. These pathologies can be classified as follows: the fifth cervical vertebra, the scapula, several ribs and the ischium are probably traumatic, and a callus on the shaft of the left pedal phalanx II-2 is probably traumatic-infectious. Traumatically fractured elements exposed to frequent movement (e.g., the scapula and the ribs show a tendency to develop pseudarthroses instead of a callus. The pathologies in the lower jaw and a reduced extensor tubercle of the left pedal phalanx II-2 are most likely traumatic or developmental in origin. The pathologies on the fourth cervical are most likely developmental in origin or idiopathic, that on the left humerus could be traumatic, developmental, infectious or idiopathic, whereas the left pedal phalanx IV-1 is classified as idiopathic. With exception of the ischium, all as traumatic/traumatic-infectious classified pathologic elements show unambiguous evidences of healing, indicating that the respective pathologies did not cause the death of this individual. Alignment of the scapula and rib pathologies from the left side suggests that all may have been caused by a single traumatic event. The ischial fracture may have been fatal. The occurrence of multiple lesions interpreted as traumatic pathologies again underlines that large-bodied theropods experienced frequent injuries during life, indicating an active predatory lifestyle, and their survival perhaps supports a gregarious behavior for Allosaurus. Alternatively, the frequent survival of traumatic events could be also related to the presence of non-endothermic metabolic rates that allow survival based on sporadic food consumption or scavenging behavior. Signs of pathologies consistent with infections are scarce and locally restricted, indicating a successful prevention of the spread of pathogens, as it is the case in extant reptiles (including birds.

  18. A new hadrosauroid (Dinosauria: Ornithopoda from the Allen Formation (Late Cretaceous of Patagonia, Argentina

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    Rubén D. Juárez Valieri

    2010-12-01

    Full Text Available A new hadrosauroid taxon from the Late Cretaceous Allen Formation is erected, on the basis of abundant cranial and postcranial material from the Salitral Moreno locality of the Rio Negro Province, Argentina. The new taxon is here named as Willinakaqe salitralensis gen. et sp. nov., which is characterized by having an autapomorphous premaxilla with a long and convex rostrolateral surface rostral to the narial fossa and associated postcrania developing an unique character combination, including: dorsal vertebrae with a shallow fossa upon the base of the transverse processes; sacral and proximal caudal neural spines more than three times the height of the centrum; distal region of the postacetabular process of ilium ventrally deflected, among others. This new hadrosauroid closely resembles Secernosaurus koerneri, the other valid hadrosauroid species from South America, based in several synapomorphies, as: angle greater than 115° between the lateral margin of the facet for scapular articulation and the glenoid in the coracoid; supra-acetabular process of the ilium asymmetrical, caudodorsal margin of ilium with a well-defined ridge continuous with the dorsal margin of the proximal region of the postacetabular process. Moreover, previous records of Lambeosaurinae from the Late Cretaceous of South America are referred to W. salitralensis, and thus, the presence of lambeosaurines in this continent is here rejected. Accordingly, Willinakaqe salitralensis gen. et sp. nov. is currently the only hadrosauroid species reported from the Allen Formation.Se erige un nuevo taxón de hadrosauroideo del Cretácico Superior de la Formación Allen, en base a abundante material craneal y postcraneal de la localidad de Salitral Moreno, en la Provincia de Río Negro, Argentina. El nuevo taxón es denominado Willinakaqe salitralensis gen. et sp. nov., y se caracteriza por tener un premaxilar autapomórfico con una superficie rostrolateral alargada y convexa rostral a la fosa narial y postcráneos asociados con una combinación de caracteres únicos, que incluye: vértebras dorsales con una fosa poco profunda en la base de los procesos transversos, espinas neurales sacras y caudales proximales más de tres veces más altas que el centro; región distal del proceso postacetabular del ilion desviada ventralmente, entre otros. Este nuevo hadrosauroideo es muy similar a Secernosaurus koerneri, la otra especie válida de hadrosauroideo de América del Sur, con el que comparte varias sinapomorfías, como: ángulo mayor que 115 ° entre el borde lateral de la faceta articular escapular y la superficie glenoidea en el coracoides, proceso supra-acetabular del ilion asimétrico, margen caudodorsal del ilion con una cresta bien definida continua con el margen dorsal de la región proximal del proceso postacetabular. Los registros asignados anteriormente a Lambeosaurinae del Cretácico Tardío de América del Sur son referidos a Willinakaqe salitralensis gen. et sp. nov., y por lo tanto, se rechaza la presencia de lambeosaurinos en este continente. En consecuencia, Willinakaqe salitralensis gen. et sp. nov. es actualmente la única especie de hadrosauroideo reportada en la Formación Allen.

  19. The first definitive Asian spinosaurid (Dinosauria: Theropoda) from the early cretaceous of Laos

    Science.gov (United States)

    Allain, Ronan; Xaisanavong, Tiengkham; Richir, Philippe; Khentavong, Bounsou

    2012-05-01

    Spinosaurids are among the largest and most specialized carnivorous dinosaurs. The morphology of their crocodile-like skull, stomach contents, and oxygen isotopic composition of the bones suggest they had a predominantly piscivorous diet. Even if close relationships between spinosaurids and Middle Jurassic megalosaurs seem well established, very little is known about the transition from a generalized large basal tetanuran to the specialized morphology of spinosaurids. Spinosaurid remains were previously known from the Early to Late Cretaceous of North Africa, Europe, and South America. Here, we report the discovery of a new spinosaurid theropod from the late Early Cretaceous Savannakhet Basin in Laos, which is distinguished by an autapomorphic sinusoidal dorsosacral sail. This new taxon, Ichthyovenator laosensis gen. et sp. nov., includes well-preserved and partially articulated postcranial remains. Although possible spinosaurid teeth have been reported from various Early Cretaceous localities in Asia, the new taxon I. laosensis is the first definite record of Spinosauridae from Asia. Cladistic analysis identifies Ichthyovenator as a member of the sub-clade Baryonychinae and suggests a widespread distribution of this clade at the end of the Early Cretaceous. Chilantaisaurus tashouikensis from the Cretaceous of Inner Mongolia, and an ungual phalanx from the Upper Jurassic of Colorado are also referred to spinosaurids, extending both the stratigraphical and geographical range of this clade.

  20. A specimen-level phylogenetic analysis and taxonomic revision of Diplodocidae (Dinosauria, Sauropoda)

    Science.gov (United States)

    Mateus, Octávio; Benson, Roger B.J.

    2015-01-01

    Diplodocidae are among the best known sauropod dinosaurs. Several species were described in the late 1800s or early 1900s from the Morrison Formation of North America. Since then, numerous additional specimens were recovered in the USA, Tanzania, Portugal, and Argentina, as well as possibly Spain, England, Georgia, Zimbabwe, and Asia. To date, the clade includes about 12 to 15 nominal species, some of them with questionable taxonomic status (e.g., ‘Diplodocus’ hayi or Dyslocosaurus polyonychius), and ranging in age from Late Jurassic to Early Cretaceous. However, intrageneric relationships of the iconic, multi-species genera Apatosaurus and Diplodocus are still poorly known. The way to resolve this issue is a specimen-based phylogenetic analysis, which has been previously implemented for Apatosaurus, but is here performed for the first time for the entire clade of Diplodocidae. The analysis includes 81 operational taxonomic units, 49 of which belong to Diplodocidae. The set of OTUs includes all name-bearing type specimens previously proposed to belong to Diplodocidae, alongside a set of relatively complete referred specimens, which increase the amount of anatomically overlapping material. Non-diplodocid outgroups were selected to test the affinities of potential diplodocid specimens that have subsequently been suggested to belong outside the clade. The specimens were scored for 477 morphological characters, representing one of the most extensive phylogenetic analyses of sauropod dinosaurs. Character states were figured and tables given in the case of numerical characters. The resulting cladogram recovers the classical arrangement of diplodocid relationships. Two numerical approaches were used to increase reproducibility in our taxonomic delimitation of species and genera. This resulted in the proposal that some species previously included in well-known genera like Apatosaurus and Diplodocus are generically distinct. Of particular note is that the famous genus Brontosaurus is considered valid by our quantitative approach. Furthermore, “Diplodocus” hayi represents a unique genus, which will herein be called Galeamopus gen. nov. On the other hand, these numerical approaches imply synonymization of “Dinheirosaurus” from the Late Jurassic of Portugal with the Morrison Formation genus Supersaurus. Our use of a specimen-, rather than species-based approach increases knowledge of intraspecific and intrageneric variation in diplodocids, and the study demonstrates how specimen-based phylogenetic analysis is a valuable tool in sauropod taxonomy, and potentially in paleontology and taxonomy as a whole. PMID:25870766

  1. The muscle-powered bite of allosaurus (dinosauria; theropoda: an interpretation of cranio-dental morphology

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    Turner, A.

    2003-12-01

    Full Text Available The skull morphology of Allosaurus has been the subject of functional interpretations which imply a predatory behaviour radically different from that recorded in any predatory land vertebrate. Those interpretations imply the use of the skull and maxillary dentition as analogues of hand-held, man-made weapons, incorporating the inertia of the predator's dash toward prey to add to the effect of the impact, and using wide jaw gapes as a way to keep the mandible out of the way of such blows. We re-interpret the evident adaptations for gape and for recruitment of neck muscles in head depression of Allosaurus in terms of a muscle-powered bite directed at surfaces with moderate convexity, such as the bodies of very large pres. In our model, the forces leading to penetration of the teeth are generated in the context of the opposition between the maxillary and the mandible. This interpretation allows us to incorporate al1 the observed adaptations of the Allosaurus skull, while avoiding the problems created by previous models.La morfología craneal de Allosaurus ha sido objeto de interpretaciones funcionales que implican un comportamiento depredador radicalmente distinto para el inferido para cualquier vertebrado depredador terrestre. Esas interpretaciones implican el uso de la dentición superior e inferior como análogos de cuchillos o dagas manufacturadas por el hombre, incorporando la inercia del golpe del depredador contra la presa para añadir el efecto del impacto, y usando amplias aperturas mandibulares para mantener la mandíbula fuera de la línea de acción del impacto. Reinterpretamos las evidentes adaptaciones para amplias aberturas mandibulares, y para la utilización de la musculatura cervical en la depresih de la cabeza de Allosaurus en función de una mordida basada en la fuerza muscular dirigida a superficies moderadamente convexas, como el cuerpo de una gran presa. En nuestro modelo, las fuerzas que producen la penetración son generadas en el contexto de una oposición entre el maxilar y la mandíbula. Esta interpretación nos permite incorporar todas las adaptaciones observadas en el cráneo de Allosaurus, al mismo tiempo que se evitan los problemas creados por modelos alternativos.

  2. A New Sail-Backed Styracosternan (Dinosauria: Ornithopoda) from the Early Cretaceous of Morella, Spain.

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    Gasulla, José Miguel; Escaso, Fernando; Narváez, Iván; Ortega, Francisco; Sanz, José Luis

    2015-01-01

    A new styracosternan ornithopod genus and species is here described based on a partial postcranial skeleton and an associated dentary tooth of a single specimen from the Arcillas de Morella Formation (Early Cretaceous, late Barremian) at the Morella locality, (Castellón, Spain). Morelladon beltrani gen. et sp. nov. is diagnosed by eight autapomorphic features. The set of autapomorphies includes: very elongated and vertical neural spines of the dorsal vertebrae, midline keel on ventral surface of the second to fourth sacral vertebrae restricted to the anterior half of the centrum, a posterodorsally inclined medial ridge on the postacetabular process of the ilium that meets its dorsal margin and distal end of the straight ischial shaft laterally expanded, among others. Phylogenetic analyses reveal that the new Iberian form is more closely related to its synchronic and sympatric contemporary European taxa Iguanodon bernissartensis and Mantellisaurus atherfieldensis, known from Western Europe, than to other Early Cretaceous Iberian styracosternans (Delapparentia turolensis and Proa valdearinnoensis). The recognition of Morelladon beltrani gen. et sp. nov. indicates that the Iberian Peninsula was home to a highly diverse medium to large bodied styracosternan assemblage during the Early Cretaceous.

  3. A large abelisaurid (Dinosauria, Theropoda from Morocco and comments on the Cenomanian theropods from North Africa

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    Alfio Alessandro Chiarenza

    2016-02-01

    Full Text Available We describe the partially preserved femur of a large-bodied theropod dinosaur from the Cenomanian “Kem Kem Compound Assemblage” (KKCA of Morocco. The fossil is housed in the Museo Geologico e Paleontologico “Gaetano Giorgio Gemmellaro” in Palermo (Italy. The specimen is compared with the theropod fossil record from the KKCA and coeval assemblages from North Africa. The combination of a distally reclined head, a not prominent trochanteric shelf, distally placed lesser trochanter of stout, alariform shape, a stocky shaft with the fourth trochanter placed proximally, and rugose muscular insertion areas in the specimen distinguishes it from Carcharodontosaurus, Deltadromeus and Spinosaurus and supports referral to an abelisaurid. The estimated body size for the individual from which this femur was derived is comparable to Carnotaurus and Ekrixinatosaurus (up to 9 meters in length and 2 tons in body mass. This find confirms that abelisaurids had reached their largest body size in the “middle Cretaceous,” and that large abelisaurids coexisted with other giant theropods in Africa. We review the taxonomic status of the theropods from the Cenomanian of North Africa, and provisionally restrict the Linnean binomina Carcharodontosaurus iguidensis and Spinosaurus aegyptiacus to the type specimens. Based on comparisons among the theropod records from the Aptian-Cenomanian of South America and Africa, a partial explanation for the so-called “Stromer’s riddle” (namely, the coexistence of many large predatory dinosaurs in the “middle Cretaceous” record from North Africa is offered in term of taphonomic artifacts among lineage records that were ecologically and environmentally non-overlapping. Although morphofunctional and stratigraphic evidence supports an ecological segregation between spinosaurids and the other lineages, the co-occurrence of abelisaurids and carcharodontosaurids, two groups showing several craniodental convergences that suggest direct resource competition, remains to be explained.

  4. First discovery of a theropod (Dinosauria) from the Upper Jurassic in Mongolia and its stratigraphy

    OpenAIRE

    MAHITO, WATANABE; Khishigjav, Tsogtbaatar; RINCHEN, BARSBOLD; Center for Paleobiological Research, Hayashibara Biochemical Laboratories, Inc.; Mongolian Paleontological Center, Mongolian Academy of Sciences

    2008-01-01

    A theropod dinosaur is described for the first time from the Upper Jurassic of Mongolia. It is represented by a partial skull from the upper Jurassic Dariv Suite in Dariv, Ikhes Nuur Basin, Gobi-Altai Aimag, western Mongolia, situated relatively close to the Xinjiang Uygur Autonomous Province in the western part of China. From the same beds of the locality, sauropod bones were also abundantly found. Those fossil discoveries suggest that both carnivorous and herbivorous dinosaurs existed in th...

  5. A New Megaraptoran Dinosaur (Dinosauria, Theropoda, Megaraptoridae) from the Late Cretaceous of Patagonia

    Science.gov (United States)

    2016-01-01

    A skeleton discovered in the Upper Cretaceous Sierra Barrosa Formation (Turonian-Coniacian) of Neuquén Province, Argentina represents a new species of theropod dinosaur related to the long snouted, highly pneumatized Megaraptoridae. The holotype specimen of Murusraptor barrosaensis n.gen et n.sp. (MCF-PVPH-411) includes much of the skull, axial skeleton, pelvis and tibia. Murusraptor is unique in having several diagnostic features that include anterodorsal process of lacrimal longer than height of preorbital process, and a thick, shelf-like thickening on the lateral surface of surangular ventral to the groove between the anterior surangular foramen and the insert for the uppermost intramandibular process of the dentary. Other characteristic features of Murusraptor barrosaensis n.gen. et n. sp.include a large mandibular fenestra, distal ends of caudal neural spines laterally thickened into lateral knob-like processes, short ischia distally flattened and slightly expanded dorsoventrally. Murusraptor belongs to a Patagonian radiation of megaraptorids together with Aerosteon, Megaraptor and Orkoraptor. In spite being immature, it is a larger but more gracile animal than existing specimens of Megaraptor, and is comparable in size with Aerosteon and Orkoraptor. The controversial phylogeny of the Megaraptoridae as members of the Allosauroidea or a clade of Coelurosauria is considered analyzing two alternative data sets. PMID:27439002

  6. A new basal titanosaur (Dinosauria, Sauropoda) from the Lower Cretaceous of Brazil

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    Carvalho, Ismar de Souza; Salgado, Leonardo; Lindoso, Rafael Matos; Araújo-Júnior, Hermínio Ismael de; Nogueira, Francisco Cézar Costa; Soares, José Agnelo

    2017-04-01

    Although dinosaurian ichnofaunas are common in the Northeastern Brazilian Interior Basins, osteological remains are poorly represented in these areas. One of the main challenges in vertebrate paleontology in the Lower Cretaceous of this region is to recognize body-fossils, which can unveil the anatomy, functional morphology and paleoecological aspects of the dinosaurian fauna recorded until now only by footprints and trackways. The discovery of a new dinosaur specimen in the Rio Piranhas Formation of the Triunfo Basin opens new perspectives into the comprehension of paleogeographical and temporal distribution of the titanosaur sauropods. Titanosaurs are common in Upper Cretaceous rocks of Brazil and Argentina. The age of the Rio Piranhas Formation is considered to range from Berriasian to early Hauterivian. Thus, the description of this new species opens new viewpoints concerning the paleobiogeographical aspects of these sauropod dinosaurs.

  7. A nomenclature for vertebral fossae in sauropods and other saurischian dinosaurs.

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    Jeffrey A Wilson

    Full Text Available BACKGROUND: The axial skeleton of extinct saurischian dinosaurs (i.e., theropods, sauropodomorphs, like living birds, was pneumatized by epithelial outpocketings of the respiratory system. Pneumatic signatures in the vertebral column of fossil saurischians include complex branching chambers within the bone (internal pneumaticity and large chambers visible externally that are bounded by neural arch laminae (external pneumaticity. Although general aspects of internal pneumaticity are synapomorphic for saurischian subgroups, the individual internal pneumatic spaces cannot be homologized across species or even along the vertebral column, due to their variability and absence of topographical landmarks. External pneumatic structures, in contrast, are defined by ready topological landmarks (vertebral laminae, but no consistent nomenclatural system exists. This deficiency has fostered confusion and limited their use as character data in phylogenetic analysis. METHODOLOGY/PRINCIPAL FINDINGS: We present a simple system for naming external neural arch fossae that parallels the one developed for the vertebral laminae that bound them. The nomenclatural system identifies fossae by pointing to reference landmarks (e.g., neural spine, centrum, costal articulations, zygapophyses. We standardize the naming process by creating tripartite names from "primary landmarks," which form the zygodiapophyseal table, "secondary landmarks," which orient with respect to that table, and "tertiary landmarks," which further delineate a given fossa. CONCLUSIONS/SIGNIFICANCE: The proposed nomenclatural system for lamina-bounded fossae adds clarity to descriptions of complex vertebrae and allows these structures to be sourced as character data for phylogenetic analyses. These anatomical terms denote potentially homologous pneumatic structures within Saurischia, but they could be applied to any vertebrate with vertebral laminae that enclose spaces, regardless of their developmental

  8. Temporal and phylogenetic evolution of the sauropod dinosaur body plan

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    Bates, Karl T.; Mannion, Philip D.; Falkingham, Peter L.; Brusatte, Stephen L.; Hutchinson, John R.; Otero, Alejandro; Sellers, William I.; Sullivan, Corwin; Stevens, Kent A.; Allen, Vivian

    2016-03-01

    The colossal size and body plan of sauropod dinosaurs are unparalleled in terrestrial vertebrates. However, to date, there have been only limited attempts to examine temporal and phylogenetic patterns in the sauropod bauplan. Here, we combine three-dimensional computational models with phylogenetic reconstructions to quantify the evolution of whole-body shape and body segment properties across the sauropod radiation. Limitations associated with the absence of soft tissue preservation in fossils result in large error bars about mean absolute body shape predictions. However, applying any consistent skeleton : body volume ratio to all taxa does yield changes in body shape that appear concurrent with major macroevolutionary events in sauropod history. A caudad shift in centre-of-mass (CoM) in Middle Triassic Saurischia, associated with the evolution of bipedalism in various dinosaur lineages, was reversed in Late Triassic sauropodomorphs. A craniad CoM shift coincided with the evolution of quadrupedalism in the Late Triassic, followed by a more striking craniad shift in Late Jurassic-Cretaceous titanosauriforms, which included the largest sauropods. These craniad CoM shifts are strongly correlated with neck enlargement, a key innovation in sauropod evolution and pivotal to their gigantism. By creating a much larger feeding envelope, neck elongation is thought to have increased feeding efficiency and opened up trophic niches that were inaccessible to other herbivores. However, we find that relative neck size and CoM position are not strongly correlated with inferred feeding habits. Instead the craniad CoM positions of titanosauriforms appear closely linked with locomotion and environmental distributions, potentially contributing to the continued success of this group until the end-Cretaceous, with all other sauropods having gone extinct by the early Late Cretaceous.

  9. Common functional correlates of head-strike behavior in the pachycephalosaur Stegoceras validum (Ornithischia, Dinosauria and combative artiodactyls.

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    Eric Snively

    Full Text Available BACKGROUND: Pachycephalosaurs were bipedal herbivorous dinosaurs with bony domes on their heads, suggestive of head-butting as seen in bighorn sheep and musk oxen. Previous biomechanical studies indicate potential for pachycephalosaur head-butting, but bone histology appears to contradict the behavior in young and old individuals. Comparing pachycephalosaurs with fighting artiodactyls tests for common correlates of head-butting in their cranial structure and mechanics. METHODS/PRINCIPAL FINDINGS: Computed tomographic (CT scans and physical sectioning revealed internal cranial structure of ten artiodactyls and pachycephalosaurs Stegoceras validum and Prenocephale prenes. Finite element analyses (FEA, incorporating bone and keratin tissue types, determined cranial stress and strain from simulated head impacts. Recursive partition analysis quantified strengths of correlation between functional morphology and actual or hypothesized behavior. Strong head-strike correlates include a dome-like cephalic morphology, neurovascular canals exiting onto the cranium surface, large neck muscle attachments, and dense cortical bone above a sparse cancellous layer in line with the force of impact. The head-butting duiker Cephalophus leucogaster is the closest morphological analog to Stegoceras, with a smaller yet similarly rounded dome. Crania of the duiker, pachycephalosaurs, and bighorn sheep Ovis canadensis share stratification of thick cortical and cancellous layers. Stegoceras, Cephalophus, and musk ox crania experience lower stress and higher safety factors for a given impact force than giraffe, pronghorn, or the non-combative llama. CONCLUSIONS/SIGNIFICANCE: Anatomy, biomechanics, and statistical correlation suggest that some pachycephalosaurs were as competent at head-to-head impacts as extant analogs displaying such combat. Large-scale comparisons and recursive partitioning can greatly refine inference of behavioral capability for fossil animals.

  10. A Basal Lithostrotian Titanosaur (Dinosauria: Sauropoda) with a Complete Skull: Implications for the Evolution and Paleobiology of Titanosauria

    Science.gov (United States)

    Martínez, Rubén D. F.; Lamanna, Matthew C.; Novas, Fernando E.; Ridgely, Ryan C.; Casal, Gabriel A.; Martínez, Javier E.; Vita, Javier R.; Witmer, Lawrence M.

    2016-01-01

    We describe Sarmientosaurus musacchioi gen. et sp. nov., a titanosaurian sauropod dinosaur from the Upper Cretaceous (Cenomanian—Turonian) Lower Member of the Bajo Barreal Formation of southern Chubut Province in central Patagonia, Argentina. The holotypic and only known specimen consists of an articulated, virtually complete skull and part of the cranial and middle cervical series. Sarmientosaurus exhibits the following distinctive features that we interpret as autapomorphies: (1) maximum diameter of orbit nearly 40% rostrocaudal length of cranium; (2) complex maxilla—lacrimal articulation, in which the lacrimal clasps the ascending ramus of the maxilla; (3) medial edge of caudal sector of maxillary ascending ramus bordering bony nasal aperture with low but distinct ridge; (4) ‘tongue-like’ ventral process of quadratojugal that overlaps quadrate caudally; (5) separate foramina for all three branches of the trigeminal nerve; (6) absence of median venous canal connecting infundibular region to ventral part of brainstem; (7) subvertical premaxillary, procumbent maxillary, and recumbent dentary teeth; (8) cervical vertebrae with ‘strut-like’ centroprezygapophyseal laminae; (9) extremely elongate and slender ossified tendon positioned ventrolateral to cervical vertebrae and ribs. The cranial endocast of Sarmientosaurus preserves some of the most complete information obtained to date regarding the brain and sensory systems of sauropods. Phylogenetic analysis recovers the new taxon as a basal member of Lithostrotia, as the most plesiomorphic titanosaurian to be preserved with a complete skull. Sarmientosaurus provides a wealth of new cranial evidence that reaffirms the close relationship of titanosaurs to Brachiosauridae. Moreover, the presence of the relatively derived lithostrotian Tapuiasaurus in Aptian deposits indicates that the new Patagonian genus represents a ‘ghost lineage’ with a comparatively plesiomorphic craniodental form, the evolutionary history of which is missing for at least 13 million years of the Cretaceous. The skull anatomy of Sarmientosaurus suggests that multiple titanosaurian species with dissimilar cranial structures coexisted in the early Late Cretaceous of southern South America. Furthermore, the new taxon possesses a number of distinctive morphologies—such as the ossified cervical tendon, extremely pneumatized cervical vertebrae, and a habitually downward-facing snout—that have rarely, if ever, been documented in other titanosaurs, thus broadening our understanding of the anatomical diversity of this remarkable sauropod clade. The latter two features were convergently acquired by at least one penecontemporaneous diplodocoid, and may represent mutual specializations for consuming low-growing vegetation. PMID:27115989

  11. A Basal Lithostrotian Titanosaur (Dinosauria: Sauropoda with a Complete Skull: Implications for the Evolution and Paleobiology of Titanosauria.

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    Rubén D F Martínez

    Full Text Available We describe Sarmientosaurus musacchioi gen. et sp. nov., a titanosaurian sauropod dinosaur from the Upper Cretaceous (Cenomanian-Turonian Lower Member of the Bajo Barreal Formation of southern Chubut Province in central Patagonia, Argentina. The holotypic and only known specimen consists of an articulated, virtually complete skull and part of the cranial and middle cervical series. Sarmientosaurus exhibits the following distinctive features that we interpret as autapomorphies: (1 maximum diameter of orbit nearly 40% rostrocaudal length of cranium; (2 complex maxilla-lacrimal articulation, in which the lacrimal clasps the ascending ramus of the maxilla; (3 medial edge of caudal sector of maxillary ascending ramus bordering bony nasal aperture with low but distinct ridge; (4 'tongue-like' ventral process of quadratojugal that overlaps quadrate caudally; (5 separate foramina for all three branches of the trigeminal nerve; (6 absence of median venous canal connecting infundibular region to ventral part of brainstem; (7 subvertical premaxillary, procumbent maxillary, and recumbent dentary teeth; (8 cervical vertebrae with 'strut-like' centroprezygapophyseal laminae; (9 extremely elongate and slender ossified tendon positioned ventrolateral to cervical vertebrae and ribs. The cranial endocast of Sarmientosaurus preserves some of the most complete information obtained to date regarding the brain and sensory systems of sauropods. Phylogenetic analysis recovers the new taxon as a basal member of Lithostrotia, as the most plesiomorphic titanosaurian to be preserved with a complete skull. Sarmientosaurus provides a wealth of new cranial evidence that reaffirms the close relationship of titanosaurs to Brachiosauridae. Moreover, the presence of the relatively derived lithostrotian Tapuiasaurus in Aptian deposits indicates that the new Patagonian genus represents a 'ghost lineage' with a comparatively plesiomorphic craniodental form, the evolutionary history of which is missing for at least 13 million years of the Cretaceous. The skull anatomy of Sarmientosaurus suggests that multiple titanosaurian species with dissimilar cranial structures coexisted in the early Late Cretaceous of southern South America. Furthermore, the new taxon possesses a number of distinctive morphologies-such as the ossified cervical tendon, extremely pneumatized cervical vertebrae, and a habitually downward-facing snout-that have rarely, if ever, been documented in other titanosaurs, thus broadening our understanding of the anatomical diversity of this remarkable sauropod clade. The latter two features were convergently acquired by at least one penecontemporaneous diplodocoid, and may represent mutual specializations for consuming low-growing vegetation.

  12. A New Oviraptorid Dinosaur (Dinosauria: Oviraptorosauria) from the Late Cretaceous of Southern China and Its Paleobiogeographical Implications.

    Science.gov (United States)

    Lü, Junchang; Pu, Hanyong; Kobayashi, Yoshitsugu; Xu, Li; Chang, Huali; Shang, Yuhua; Liu, Di; Lee, Yuong-Nam; Kundrát, Martin; Shen, Caizhi

    2015-07-02

    The Ganzhou area of Jiangxi Province, southern China is becoming one of the most productive oviraptorosaurian localities in the world. A new oviraptorid dinosaur was unearthed from the uppermost Upper Cretaceous Nanxiong Formation of Ganzhou area. It is characterized by an anterodorsally sloping occiput and quadrate (a feature shared with Citipati), a circular supratemporal fenestra that is much smaller than the lower temporal fenestra, and a dentary in which the dorsal margin above the external mandibular fenestra is strongly concave ventrally. The position of the anteroventral corner of the external naris in relation to the posterodorsal corner of the antorbital fenestra provides new insight into the craniofacial evolution of oviraptorosaurid dinosaurs. A phylogenetic analysis recovers the new taxon as closely related to the Mongolian Citipati. Six oviraptorid dinosaurs from the Nanxiong Formation (Ganzhou and Nanxiong) are distributed within three clades of the family. Each of the three clades from the Nanxiong Formation has close relatives in Inner Mongolia and Mongolia, and in both places each clade may have had a specific diet or occupied a different ecological niche. Oviraptorid dinosaurs were geographically widespread across Asia in the latest Cretaceous and were an important component of terrestrial ecosystems during this time.

  13. New information on the cranial anatomy of Acrocanthosaurus atokensis and its implications for the phylogeny of Allosauroidea (Dinosauria: Theropoda).

    Science.gov (United States)

    Eddy, Drew R; Clarke, Julia A

    2011-03-21

    Allosauroidea has a contentious taxonomic and systematic history. Within this group of theropod dinosaurs, considerable debate has surrounded the phylogenetic position of the large-bodied allosauroid Acrocanthosaurus atokensis from the Lower Cretaceous Antlers Formation of North America. Several prior analyses recover Acrocanthosaurus atokensis as sister taxon to the smaller-bodied Allosaurus fragilis known from North America and Europe, and others nest Acrocanthosaurus atokensis within Carcharodontosauridae, a large-bodied group of allosauroids that attained a cosmopolitan distribution during the Early Cretaceous. Re-evaluation of a well-preserved skull of Acrocanthosaurus atokensis (NCSM 14345) provides new information regarding the palatal complex and inner surfaces of the skull and mandible. Previously inaccessible internal views and articular surfaces of nearly every element of the skull are described. Twenty-four new morphological characters are identified as variable in Allosauroidea, combined with 153 previously published characters, and evaluated for eighteen terminal taxa. Systematic analysis of this dataset recovers a single most parsimonious topology placing Acrocanthosaurus atokensis as a member of Allosauroidea, in agreement with several recent analyses that nest the taxon well within Carcharodontosauridae. A revised diagnosis of Acrocanthosaurus atokensis finds that the species is distinguished by four primary characters, including: presence of a knob on the lateral surangular shelf; enlarged posterior surangular foramen; supraoccipital protruding as a double-boss posterior to the nuchal crest; and pneumatic recess within the medial surface of the quadrate. Furthermore, the recovered phylogeny more closely agrees with the stratigraphic record than hypotheses that place Acrocanthosaurus atokensis as more closely related to Allosaurus fragilis. Fitch optimization of body size is also more consistent with the placement of Acrocanthosaurus atokensis within a clade of larger carcharodontosaurid taxa than with smaller-bodied taxa near the base of Allosauroidea. This placement of Acrocanthosaurus atokensis supports previous hypotheses of a global carcharodontosaurid radiation during the Early Cretaceous.

  14. New information on the cranial anatomy of Acrocanthosaurus atokensis and its implications for the phylogeny of Allosauroidea (Dinosauria: Theropoda.

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    Drew R Eddy

    Full Text Available BACKGROUND: Allosauroidea has a contentious taxonomic and systematic history. Within this group of theropod dinosaurs, considerable debate has surrounded the phylogenetic position of the large-bodied allosauroid Acrocanthosaurus atokensis from the Lower Cretaceous Antlers Formation of North America. Several prior analyses recover Acrocanthosaurus atokensis as sister taxon to the smaller-bodied Allosaurus fragilis known from North America and Europe, and others nest Acrocanthosaurus atokensis within Carcharodontosauridae, a large-bodied group of allosauroids that attained a cosmopolitan distribution during the Early Cretaceous. METHODOLOGY/PRINCIPAL FINDINGS: Re-evaluation of a well-preserved skull of Acrocanthosaurus atokensis (NCSM 14345 provides new information regarding the palatal complex and inner surfaces of the skull and mandible. Previously inaccessible internal views and articular surfaces of nearly every element of the skull are described. Twenty-four new morphological characters are identified as variable in Allosauroidea, combined with 153 previously published characters, and evaluated for eighteen terminal taxa. Systematic analysis of this dataset recovers a single most parsimonious topology placing Acrocanthosaurus atokensis as a member of Allosauroidea, in agreement with several recent analyses that nest the taxon well within Carcharodontosauridae. CONCLUSIONS/SIGNIFICANCE: A revised diagnosis of Acrocanthosaurus atokensis finds that the species is distinguished by four primary characters, including: presence of a knob on the lateral surangular shelf; enlarged posterior surangular foramen; supraoccipital protruding as a double-boss posterior to the nuchal crest; and pneumatic recess within the medial surface of the quadrate. Furthermore, the recovered phylogeny more closely agrees with the stratigraphic record than hypotheses that place Acrocanthosaurus atokensis as more closely related to Allosaurus fragilis. Fitch optimization of body size is also more consistent with the placement of Acrocanthosaurus atokensis within a clade of larger carcharodontosaurid taxa than with smaller-bodied taxa near the base of Allosauroidea. This placement of Acrocanthosaurus atokensis supports previous hypotheses of a global carcharodontosaurid radiation during the Early Cretaceous.

  15. Arcosaurios (Crocodilia, Dinosauria del Cretácico superior de la Conca de Tremp (Lleida, España

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    Buscalioni, A. D.

    1987-12-01

    Full Text Available The study of a great part of the material found during the excavation work carried out by a team of the «Institut de Paleontología de Sabadell» and other paleontologists of the universities of Madrid and Bellaterra, in the basin of Tremp (Maastrichtiense in 1984 and 1985 has made possible the recognition of: 1.º A large sized Crocodilian, attributable to an adult animal of the Alligatoridae family, comparable to Crocodilus affluvelensis. 2.° Dinosaur remains atributed to three difIerent families: Atlantosauridae (represented by a large sized Sauropod, probably Hypselosaurus; Iguanodontidae (afI. Rhabdodon, medium sized Omithopod; and Hadrosauridae (Ortbomerus, small sized. 3.° Dinosaur's footprints, not very well preserved, medium and large sized, attributable to biped Omithopod. The fauna remains were always found unconnected, scattered all over large areas and with no signs of depredation. The sort of materials found reveal a certain transport which caused a selective action over the remains. Later, the efIects of the orogenic processes suffered by this area in the Tertiary period would combine with this transport.El estudio de gran parte del material hallado en los trabajos de excavación realizados por un equipo del «Institut de Paleontología de Sabadell» y otros paleontólogos de las Universidades de Madrid y Bellaterra, en la cuenca de Tremp (Maastrichtiense, durante los años 1984 y 1985, ha permitido reconocer: 1.º Un crocodílido de gran talla, atribuible a un animal adulto de la familia Alligatoridae, comparable a Crocodilus affluvelensis. 2.° Restos de dinosaurios que se han atribuido a tres familias: Atlantosauridae (representada por un saurópodo de gran talla, probablemente Hypselosaurus; Iguanodontidae (afI. Rhabdodon, ornitópodo de talla media, y Hadrosauridae (Ortbomerus, de talla pequeña. 3.° Icnitas de dinosaurios, bastante mal conservadas, de tamaño medio y grande, atribuibles a omitópodos bípedos. Los restos faunísticos han sido hallados siempre inconexos, esparcidos en extensas superficies y sin señales de depredación. El tipo de material hallado indica, en principio, un cierto transporte, el cual ejerció una acción selectiva sobre los restos. Posteriormente, a este transporte se unirían los efectos de los procesos orogénicos que afectaron la zona durante el Terciario.

  16. Topology, divergence dates, and macroevolutionary inferences vary between different tip-dating approaches applied to fossil theropods (Dinosauria)

    OpenAIRE

    Bapst, D. W.; Wright, A.M; Matzke, N. J.; Lloyd, G.T.

    2016-01-01

    Dated phylogenies of fossil taxa allow palaeobiologists to estimate the timing of major divergences and placement of extinct lineages, and to test macroevolutionary hypotheses. Recently developed Bayesian ?tip-dating? methods simultaneously infer and date the branching relationships among fossil taxa, and infer putative ancestral relationships. Using a previously published dataset for extinct theropod dinosaurs, we contrast the dated relationships inferred by several tip-dating approaches and...

  17. A new basal hadrosauroid dinosaur (Dinosauria: Ornithopoda) with transitional features from the late cretaceous of Henan Province, China.

    Science.gov (United States)

    Xing, Hai; Wang, Deyou; Han, Fenglu; Sullivan, Corwin; Ma, Qingyu; He, Yiming; Hone, David W E; Yan, Ronghao; Du, Fuming; Xu, Xing

    2014-01-01

    Southwestern Henan Province in central China contains many down-faulted basins, including the Xixia Basin where the Upper Cretaceous continental sediments are well exposed. The Majiacun Formation is a major dinosaur-bearing stratigraphic unit that occurs in this basin. A new basal hadrosauroid dinosaur, Zhanghenglong yangchengensis gen. et sp. nov., is named based on newly collected specimens from the middle Santonian Majiacun Formation of Zhoujiagou Village, Xixia Basin. Two transitional features between basal hadrosauroids and hadrosaurids are attached to the diagnosis of the new taxon, namely five maxillary foramina consisting of four small scattered ones anteroposteriorly arranged in a row and a large one adjacent to the articular facet for the jugal, and dentary tooth crowns bearing both median and distally offset primary ridges. Zhanghenglong also displays a unique combination of plesiomorphic and derived features of hadrosauroids, and is clearly morphologically transitional between basal hadrosauroids and hadrosaurids. Furthermore, some measurement attributes in osteology are applied to the quantitative analysis of Zhanghenglong. For these attributes, the partition of the dataset on most hadrosauroid species resulting from model-based cluster analysis almost matches taxonomic separation between basal hadrosauroids and hadrosaurids. Data of Zhanghenglong on selected measurement attributes straddle the two combinations of intervals of partitioned datasets respectively related to basal hadrosauroids and hadrosaurids. This condition is similar to mosaic evolution of morphological characters present in the specimens of the taxon. The phylogenetic analysis of Hadrosauroidea recovers a clade composed of Zhanghenglong, Nanyangosaurus, and Hadrosauridae with an unresolved polytomy. Zhanghenglong is probably a relatively derived non-hadrosaurid hadrosauroid, based on the inferences made from the morphological comparisons, quantitative evaluation of measurements, and cladistic analysis. In combination with information on the stratigraphy, phylogeny and biogeography, the material of Zhanghenglong provides direct evidence for the hypothesis that hadrosaurids might have originated in Asia.

  18. Cranial bones and atlas of titanosaurs (Dinosauria, Sauropoda) from Late Cretaceous (Bauru Group) of Uberaba, Minas Gerais State, Brazil

    Science.gov (United States)

    Martinelli, Agustín G.; Marinho, Thiago da Silva; Filippi, Leonardo S.; Ribeiro, Luiz Carlos Borges; Ferraz, Mara Lúcia da Fonseca; Cavellani, Camila Lourencini; Teixeira, Vicente de Paula Antunes

    2015-08-01

    Isolated left prefrontal, left squamosal and atlas of titanosaur dinosaurs are described and compared. They come from the Late Cretaceous Serra da Galga Member of the Marília Formation at the Serra do Veadinho region, Peirópolis (Uberaba County, Minas Gerais State, Brazil). Due to the sparse cranial elements of titanosaurs already known from Brazil, these specimens are noticeable to be presented. In addition, the atlas vertebra is described for the first time for Brazilian titanosaurs. The morphology of the cranial bones closely resembles lithostratian titanosaurs, such as Rapetosaurus, rather than basal titanosaurs. The atlas is similar to that of other titanosaurs, suggesting that the anatomy of this element seems to be more conservative than other vertebral elements, in which vertebral laminae play an important rule in titanosaur taxonomy.

  19. Homology and architecture of the caudal basket of Pachycephalosauria (Dinosauria: Ornithischia: the first occurrence of myorhabdoi in Tetrapoda.

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    Caleb Marshall Brown

    Full Text Available BACKGROUND: Associated postcranial skeletons of pachycephalosaurids, most notably those of Stegoceras and Homalocephale, reveal enigmatic osseous structures not present in other tetrapod clades. The homology and functional significance of these structures have remained elusive as they were originally interpreted to be abdominal ribs or gastralia, and more recently have been interpreted as de novo structures in the tail. PRINCIPAL FINDINGS: Analysis of these structures in nearly all pachycephalosaurid skeletons has facilitated a complete description of their architecture, and the establishment of patterns consistent with those of myorhabdoid ossifications--ossifications of the myoseptal tendons associated with myomeres. The presence and structure of myorhabdoid ossifications are well established for teleost fish, but this marks their first recognition within Tetrapoda. These elements are both structurally and histologically distinct from the deep, paraxial ossified tendon bundles of other ornithischian clades, although they may have performed a similar function in the stiffening of the tail. CONCLUSIONS/SIGNIFICANCE: These myorhabdoi are not de novo structures, but are instead ossifications (and therefore more amenable to fossilization of the normally unossified plesiomorphic caudal myosepta of vertebrates. The ubiquitous ossification of these structures in pachycephalosaurids (all specimens preserving the tail also exhibit myorhabdoid ossifications suggests it is a likely synapomorphic condition for Pachycephalosauria.

  20. Homology and Architecture of the Caudal Basket of Pachycephalosauria (Dinosauria: Ornithischia): The First Occurrence of Myorhabdoi in Tetrapoda

    OpenAIRE

    Brown, Caleb Marshall; Russell, Anthony P.

    2012-01-01

    BACKGROUND: Associated postcranial skeletons of pachycephalosaurids, most notably those of Stegoceras and Homalocephale, reveal enigmatic osseous structures not present in other tetrapod clades. The homology and functional significance of these structures have remained elusive as they were originally interpreted to be abdominal ribs or gastralia, and more recently have been interpreted as de novo structures in the tail. PRINCIPAL FINDINGS: Analysis of these structures in nearly all pachycepha...

  1. Homology and architecture of the caudal basket of Pachycephalosauria (Dinosauria: Ornithischia): the first occurrence of myorhabdoi in Tetrapoda.

    Science.gov (United States)

    Brown, Caleb Marshall; Russell, Anthony P

    2012-01-01

    Associated postcranial skeletons of pachycephalosaurids, most notably those of Stegoceras and Homalocephale, reveal enigmatic osseous structures not present in other tetrapod clades. The homology and functional significance of these structures have remained elusive as they were originally interpreted to be abdominal ribs or gastralia, and more recently have been interpreted as de novo structures in the tail. Analysis of these structures in nearly all pachycephalosaurid skeletons has facilitated a complete description of their architecture, and the establishment of patterns consistent with those of myorhabdoid ossifications--ossifications of the myoseptal tendons associated with myomeres. The presence and structure of myorhabdoid ossifications are well established for teleost fish, but this marks their first recognition within Tetrapoda. These elements are both structurally and histologically distinct from the deep, paraxial ossified tendon bundles of other ornithischian clades, although they may have performed a similar function in the stiffening of the tail. These myorhabdoi are not de novo structures, but are instead ossifications (and therefore more amenable to fossilization) of the normally unossified plesiomorphic caudal myosepta of vertebrates. The ubiquitous ossification of these structures in pachycephalosaurids (all specimens preserving the tail also exhibit myorhabdoid ossifications) suggests it is a likely synapomorphic condition for Pachycephalosauria.

  2. Vertebral Pneumaticity in the Ornithomimosaur Archaeornithomimus (Dinosauria: Theropoda Revealed by Computed Tomography Imaging and Reappraisal of Axial Pneumaticity in Ornithomimosauria.

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    Akinobu Watanabe

    Full Text Available Among extant vertebrates, pneumatization of postcranial bones is unique to birds, with few known exceptions in other groups. Through reduction in bone mass, this feature is thought to benefit flight capacity in modern birds, but its prevalence in non-avian dinosaurs of variable sizes has generated competing hypotheses on the initial adaptive significance of postcranial pneumaticity. To better understand the evolutionary history of postcranial pneumaticity, studies have surveyed its distribution among non-avian dinosaurs. Nevertheless, the degree of pneumaticity in the basal coelurosaurian group Ornithomimosauria remains poorly known, despite their potential to greatly enhance our understanding of the early evolution of pneumatic bones along the lineage leading to birds. Historically, the identification of postcranial pneumaticity in non-avian dinosaurs has been based on examination of external morphology, and few studies thus far have focused on the internal architecture of pneumatic structures inside the bones. Here, we describe the vertebral pneumaticity of the ornithomimosaur Archaeornithomimus with the aid of X-ray computed tomography (CT imaging. Complementary examination of external and internal osteology reveals (1 highly pneumatized cervical vertebrae with an elaborate configuration of interconnected chambers within the neural arch and the centrum; (2 anterior dorsal vertebrae with pneumatic chambers inside the neural arch; (3 apneumatic sacral vertebrae; and (4 a subset of proximal caudal vertebrae with limited pneumatic invasion into the neural arch. Comparisons with other theropod dinosaurs suggest that ornithomimosaurs primitively exhibited a plesiomorphic theropod condition for axial pneumaticity that was extended among later taxa, such as Archaeornithomimus and large bodied Deinocheirus. This finding corroborates the notion that evolutionary increases in vertebral pneumaticity occurred in parallel among independent lineages of bird-line archosaurs. Beyond providing a comprehensive view of vertebral pneumaticity in a non-avian coelurosaur, this study demonstrates the utility and need of CT imaging for further clarifying the early evolutionary history of postcranial pneumaticity.

  3. A New Brachylophosaurin Hadrosaur (Dinosauria: Ornithischia with an Intermediate Nasal Crest from the Campanian Judith River Formation of Northcentral Montana.

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    Elizabeth A Freedman Fowler

    Full Text Available Brachylophosaurini is a clade of hadrosaurine dinosaurs currently known from the Campanian (Late Cretaceous of North America. Its members include: Acristavus gagslarsoni, which lacks a nasal crest; Brachylophosaurus canadensis, which possesses a flat paddle-shaped nasal crest projecting posteriorly over the dorsal skull roof; and Maiasaura peeblesorum, which possesses a dorsally-projecting nasofrontal crest. Acristavus, from the lower Two Medicine Formation of Montana (~81-80 Ma, is hypothesized to be the ancestral member of the clade. Brachylophosaurus specimens are from the middle Oldman Formation of Alberta and equivalent beds in the Judith River Formation of Montana; the upper Oldman Formation is dated 77.8 Ma.A new brachylophosaurin hadrosaur, Probrachylophosaurus bergei (gen. et sp. nov. is described and phylogenetically analyzed based on the skull and postcranium of a large individual from the Judith River Formation of northcentral Montana (79.8-79.5 Ma; the horizon is equivalent to the lower Oldman Formation of Alberta. Cranial morphology of Probrachylophosaurus, most notably the nasal crest, is intermediate between Acristavus and Brachylophosaurus. In Brachylophosaurus, the nasal crest lengthens and flattens ontogenetically, covering the supratemporal fenestrae in large adults. The smaller nasal crest of Probrachylophosaurus is strongly triangular in cross section and only minimally overhangs the supratemporal fenestrae, similar to an ontogenetically earlier stage of Brachylophosaurus. Sutural fusion and tibial osteohistology reveal that the holotype of Probrachylophosaurus was relatively more mature than a similarly large Brachylophosaurus specimen; thus, Probrachylophosaurus is not simply an immature Brachylophosaurus.The small triangular posteriorly oriented nasal crest of Probrachylophosaurus is proposed to represent a transitional nasal morphology between that of a non-crested ancestor such as Acristavus and the large flat posteriorly oriented nasal crest of adult Brachylophosaurus. Because Probrachylophosaurus is stratigraphically and morphologically intermediate between these taxa, Probrachylophosaurus is hypothesized to be an intermediate member of the Acristavus-Brachylophosaurus evolutionary lineage.

  4. Cranial Anatomy of Wendiceratops pinhornensis gen. et sp. nov., a Centrosaurine Ceratopsid (Dinosauria: Ornithischia) from the Oldman Formation (Campanian), Alberta, Canada, and the Evolution of Ceratopsid Nasal Ornamentation.

    Science.gov (United States)

    Evans, David C; Ryan, Michael J

    2015-01-01

    The fossil record of ceratopsid dinosaurs between the occurrence of their proximate sister taxa in the Turonian and the beginning of their well-documented radiation from the late Campanian of North America onwards (approximately 90 and 77 Ma) is poor, with only seven taxa described from this early period in their evolution. We describe a new taxon of a highly adorned basal centrosaurine, Wendiceratops pinhornensis gen. et sp. nov., from the lower part of the Oldman Formation (middle Campanian, approximately 78-79 Ma), Alberta, Canada. Over 200 bones derived from virtually all parts of the skeleton, including multiple well-preserved specimens of the diagnostic parietosquamosal frill, were collected from a medium-density monodominant bonebed, making the new taxon one of the best-represented early ceratopsids. The new taxon is apomorphic in having epiparietals at loci 2 and 3 developed as broad-based, pachyostotic processes that are strongly procurved anterodorsally to overhang the posterior and lateral parietal rami, and an ischium with a broad, rectangular distal terminus. Although the morphology of the nasal is incompletely known, Wendiceratops is inferred to have a large, upright nasal horn located close to the orbits, which represents the oldest occurrence of this feature in Ceratopsia. Given the phylogenetic position of the new taxon within Centrosaurinae, a enlarged nasal horn is hypothesized to have arisen independently at least twice in ceratopsid evolution.

  5. A new small-bodied ornithopod (Dinosauria, Ornithischia) from a deep, high-energy Early Cretaceous river of the Australian-Antarctic rift system.

    Science.gov (United States)

    Herne, Matthew C; Tait, Alan M; Weisbecker, Vera; Hall, Michael; Nair, Jay P; Cleeland, Michael; Salisbury, Steven W

    2018-01-01

    A new small-bodied ornithopod dinosaur, Diluvicursor pickeringi , gen. et sp. nov., is named from the lower Albian of the Eumeralla Formation in southeastern Australia and helps shed new light on the anatomy and diversity of Gondwanan ornithopods. Comprising an almost complete tail and partial lower right hindlimb, the holotype (NMV P221080) was deposited as a carcass or body-part in a log-filled scour near the base of a deep, high-energy river that incised a faunally rich, substantially forested riverine floodplain within the Australian-Antarctic rift graben. The deposit is termed the 'Eric the Red West Sandstone.' The holotype, interpreted as an older juvenile ∼1.2 m in total length, appears to have endured antemortem trauma to the pes. A referred, isolated posterior caudal vertebra (NMV P229456) from the holotype locality, suggests D. pickeringi grew to at least 2.3 m in length. D. pickeringi is characterised by 10 potential autapomorphies, among which dorsoventrally low neural arches and transversely broad caudal ribs on the anterior-most caudal vertebrae are a visually defining combination of features. These features suggest D. pickeringi had robust anterior caudal musculature and strong locomotor abilities. Another isolated anterior caudal vertebra (NMV P228342) from the same deposit, suggests that the fossil assemblage hosts at least two ornithopod taxa. D. pickeringi and two stratigraphically younger, indeterminate Eumeralla Formation ornithopods from Dinosaur Cove, NMV P185992/P185993 and NMV P186047, are closely related. However, the tail of D. pickeringi is far shorter than that of NMV P185992/P185993 and its pes more robust than that of NMV P186047. Preliminary cladistic analysis, utilising three existing datasets, failed to resolve D. pickeringi beyond a large polytomy of Ornithopoda. However, qualitative assessment of shared anatomical features suggest that the Eumeralla Formation ornithopods, South American Anabisetia saldiviai and Gasparinisaura cincosaltensis , Afro-Laurasian dryosaurids and possibly Antarctic Morrosaurus antarcticus share a close phylogenetic progenitor. Future phylogenetic analysis with improved data on Australian ornithopods will help to test these suggested affinities.

  6. The Postcranial Skeleton of an Exceptionally Complete Individual of the Plated Dinosaur Stegosaurus stenops (Dinosauria: Thyreophora) from the Upper Jurassic Morrison Formation of Wyoming, U.S.A.

    Science.gov (United States)

    Maidment, Susannah Catherine Rose; Brassey, Charlotte; Barrett, Paul Michael

    2015-01-01

    Although Stegosaurus is one of the most iconic dinosaurs, well-preserved fossils are rare and as a consequence there is still much that remains unknown about the taxon. A new, exceptionally complete individual affords the opportunity to describe the anatomy of Stegosaurus in detail for the first time in over a century, and enables additional comparisons with other stegosaurian dinosaurs. The new specimen is from the Red Canyon Ranch Quarry, near Shell Wyoming, and appears to have been so well preserved because it was buried rapidly in a pond or body of standing water immediately after death. The quarry is probably located in the middle part of the Morrison Formation, which is believed to be Tithonian in age in this area. The specimen is referable to Stegosaurus stenops based on the possession of an edentulous anterior portion of the dentary and elevated postzygapophyses on the cervical vertebrae. New information provided by the specimen concerns the morphology of the vertebrae, the iliosacral block and dermal armor. Several aspects of its morphology indicate the individual was not fully skeletally mature at the time of death, corroborating a previous histological study.

  7. A Re-Evaluation of the Chasmosaurine Ceratopsid Genus Chasmosaurus (Dinosauria: Ornithischia) from the Upper Cretaceous (Campanian) Dinosaur Park Formation of Western Canada.

    Science.gov (United States)

    Campbell, James A; Ryan, Michael J; Holmes, Robert B; Schröder-Adams, Claudia J

    2016-01-01

    The chasmosaurine ceratopsid Chasmosaurus is known from the Upper Cretaceous (Campanian) Dinosaur Park Formation of southern Alberta and Saskatchewan. Two valid species, Chasmosaurus belli and C. russelli, have been diagnosed by differences in cranial ornamentation. Their validity has been supported, in part, by the reported stratigraphic segregation of chasmosaurines in the Dinosaur Park Formation, with C. belli and C. russelli occurring in discrete, successive zones within the formation. An analysis of every potentially taxonomically informative chasmosaurine specimen from the Dinosaur Park Formation indicates that C. belli and C. russelli have indistinguishable ontogenetic histories and overlapping stratigraphic intervals. Neither taxon exhibits autapomorphies, nor a unique set of apomorphies, but they can be separated and diagnosed by a single phylogenetically informative character-the embayment angle formed by the posterior parietal bars relative to the parietal midline. Although relatively deeply embayed specimens (C. russelli) generally have relatively longer postorbital horncores than specimens with more shallow embayments (C. belli), neither this horncore character nor epiparietal morphology can be used to consistently distinguish every specimen of C. belli from C. russelli. Kosmoceratops is purportedly represented in the Dinosaur Park Formation by a specimen previously referred to Chasmosaurus. The reassignment of this specimen to Kosmoceratops is unsupported here, as it is based on features that are either influenced by taphonomy or within the realm of individual variation for Chasmosaurus. Therefore, we conclude that Kosmoceratops is not present in the Dinosaur Park Formation, but is instead restricted to southern Laramidia, as originally posited.

  8. Spiclypeus shipporum gen. et sp. nov., a Boldly Audacious New Chasmosaurine Ceratopsid (Dinosauria: Ornithischia from the Judith River Formation (Upper Cretaceous: Campanian of Montana, USA.

    Directory of Open Access Journals (Sweden)

    Jordan C Mallon

    Full Text Available This study reports on a new ceratopsid, Spiclypeus shipporum gen et sp. nov., from the lower Coal Ridge Member of the Judith River Formation in Montana, USA, which dates to ~76 Ma (upper Campanian. The species is distinguished by rugose dorsal contacts on the premaxillae for the nasals, laterally projecting postorbital horncores, fully fused and anteriorly curled P1 and P2 epiparietals, and a posterodorsally projecting P3 epiparietal. The holotype specimen is also notable for its pathological left squamosal and humerus, which show varied signs of osteomyelitis and osteoarthritis. Although the postorbital horncores of Spiclypeus closely resemble those of the contemporaneous 'Ceratops', the horncores of both genera are nevertheless indistinguishable from those of some other horned dinosaurs, including Albertaceratops and Kosmoceratops; 'Ceratops' is therefore maintained as a nomen dubium. Cladistic analysis recovers Spiclypeus as the sister taxon to the clade Vagaceratops + Kosmoceratops, and appears transitional in the morphology of its epiparietals. The discovery of Spiclypeus adds to the poorly known dinosaur fauna of the Judith River Formation, and suggests faunal turnover within the formation.

  9. Spiclypeus shipporum gen. et sp. nov., a Boldly Audacious New Chasmosaurine Ceratopsid (Dinosauria: Ornithischia) from the Judith River Formation (Upper Cretaceous: Campanian) of Montana, USA.

    Science.gov (United States)

    Mallon, Jordan C; Ott, Christopher J; Larson, Peter L; Iuliano, Edward M; Evans, David C

    2016-01-01

    This study reports on a new ceratopsid, Spiclypeus shipporum gen et sp. nov., from the lower Coal Ridge Member of the Judith River Formation in Montana, USA, which dates to ~76 Ma (upper Campanian). The species is distinguished by rugose dorsal contacts on the premaxillae for the nasals, laterally projecting postorbital horncores, fully fused and anteriorly curled P1 and P2 epiparietals, and a posterodorsally projecting P3 epiparietal. The holotype specimen is also notable for its pathological left squamosal and humerus, which show varied signs of osteomyelitis and osteoarthritis. Although the postorbital horncores of Spiclypeus closely resemble those of the contemporaneous 'Ceratops', the horncores of both genera are nevertheless indistinguishable from those of some other horned dinosaurs, including Albertaceratops and Kosmoceratops; 'Ceratops' is therefore maintained as a nomen dubium. Cladistic analysis recovers Spiclypeus as the sister taxon to the clade Vagaceratops + Kosmoceratops, and appears transitional in the morphology of its epiparietals. The discovery of Spiclypeus adds to the poorly known dinosaur fauna of the Judith River Formation, and suggests faunal turnover within the formation.

  10. The Postcranial Skeleton of an Exceptionally Complete Individual of the Plated Dinosaur Stegosaurus stenops (Dinosauria: Thyreophora from the Upper Jurassic Morrison Formation of Wyoming, U.S.A.

    Directory of Open Access Journals (Sweden)

    Susannah Catherine Rose Maidment

    Full Text Available Although Stegosaurus is one of the most iconic dinosaurs, well-preserved fossils are rare and as a consequence there is still much that remains unknown about the taxon. A new, exceptionally complete individual affords the opportunity to describe the anatomy of Stegosaurus in detail for the first time in over a century, and enables additional comparisons with other stegosaurian dinosaurs. The new specimen is from the Red Canyon Ranch Quarry, near Shell Wyoming, and appears to have been so well preserved because it was buried rapidly in a pond or body of standing water immediately after death. The quarry is probably located in the middle part of the Morrison Formation, which is believed to be Tithonian in age in this area. The specimen is referable to Stegosaurus stenops based on the possession of an edentulous anterior portion of the dentary and elevated postzygapophyses on the cervical vertebrae. New information provided by the specimen concerns the morphology of the vertebrae, the iliosacral block and dermal armor. Several aspects of its morphology indicate the individual was not fully skeletally mature at the time of death, corroborating a previous histological study.

  11. Cranial Anatomy of Wendiceratops pinhornensis gen. et sp. nov., a Centrosaurine Ceratopsid (Dinosauria: Ornithischia from the Oldman Formation (Campanian, Alberta, Canada, and the Evolution of Ceratopsid Nasal Ornamentation.

    Directory of Open Access Journals (Sweden)

    David C Evans

    Full Text Available The fossil record of ceratopsid dinosaurs between the occurrence of their proximate sister taxa in the Turonian and the beginning of their well-documented radiation from the late Campanian of North America onwards (approximately 90 and 77 Ma is poor, with only seven taxa described from this early period in their evolution. We describe a new taxon of a highly adorned basal centrosaurine, Wendiceratops pinhornensis gen. et sp. nov., from the lower part of the Oldman Formation (middle Campanian, approximately 78-79 Ma, Alberta, Canada. Over 200 bones derived from virtually all parts of the skeleton, including multiple well-preserved specimens of the diagnostic parietosquamosal frill, were collected from a medium-density monodominant bonebed, making the new taxon one of the best-represented early ceratopsids. The new taxon is apomorphic in having epiparietals at loci 2 and 3 developed as broad-based, pachyostotic processes that are strongly procurved anterodorsally to overhang the posterior and lateral parietal rami, and an ischium with a broad, rectangular distal terminus. Although the morphology of the nasal is incompletely known, Wendiceratops is inferred to have a large, upright nasal horn located close to the orbits, which represents the oldest occurrence of this feature in Ceratopsia. Given the phylogenetic position of the new taxon within Centrosaurinae, a enlarged nasal horn is hypothesized to have arisen independently at least twice in ceratopsid evolution.

  12. A new small-bodied ornithopod (Dinosauria, Ornithischia from a deep, high-energy Early Cretaceous river of the Australian–Antarctic rift system

    Directory of Open Access Journals (Sweden)

    Matthew C. Herne

    2018-01-01

    Full Text Available A new small-bodied ornithopod dinosaur, Diluvicursor pickeringi, gen. et sp. nov., is named from the lower Albian of the Eumeralla Formation in southeastern Australia and helps shed new light on the anatomy and diversity of Gondwanan ornithopods. Comprising an almost complete tail and partial lower right hindlimb, the holotype (NMV P221080 was deposited as a carcass or body-part in a log-filled scour near the base of a deep, high-energy river that incised a faunally rich, substantially forested riverine floodplain within the Australian–Antarctic rift graben. The deposit is termed the ‘Eric the Red West Sandstone.’ The holotype, interpreted as an older juvenile ∼1.2 m in total length, appears to have endured antemortem trauma to the pes. A referred, isolated posterior caudal vertebra (NMV P229456 from the holotype locality, suggests D. pickeringi grew to at least 2.3 m in length. D. pickeringi is characterised by 10 potential autapomorphies, among which dorsoventrally low neural arches and transversely broad caudal ribs on the anterior-most caudal vertebrae are a visually defining combination of features. These features suggest D. pickeringi had robust anterior caudal musculature and strong locomotor abilities. Another isolated anterior caudal vertebra (NMV P228342 from the same deposit, suggests that the fossil assemblage hosts at least two ornithopod taxa. D. pickeringi and two stratigraphically younger, indeterminate Eumeralla Formation ornithopods from Dinosaur Cove, NMV P185992/P185993 and NMV P186047, are closely related. However, the tail of D. pickeringi is far shorter than that of NMV P185992/P185993 and its pes more robust than that of NMV P186047. Preliminary cladistic analysis, utilising three existing datasets, failed to resolve D. pickeringi beyond a large polytomy of Ornithopoda. However, qualitative assessment of shared anatomical features suggest that the Eumeralla Formation ornithopods, South American Anabisetia saldiviai and Gasparinisaura cincosaltensis, Afro-Laurasian dryosaurids and possibly Antarctic Morrosaurus antarcticus share a close phylogenetic progenitor. Future phylogenetic analysis with improved data on Australian ornithopods will help to test these suggested affinities.

  13. An ornithomimid (Dinosauria) bonebed from the Late Cretaceous of Alberta, with implications for the behavior, classification, and stratigraphy of North American ornithomimids.

    Science.gov (United States)

    Cullen, Thomas M; Ryan, Michael J; Schröder-Adams, Claudia; Currie, Philip J; Kobayashi, Yoshitsugu

    2013-01-01

    Bonebeds can provide a wealth of anatomical, taphonomic, and ontogenetic information about the specimens preserved within them, and can provide evidence for inferred behavior. The material described here represents the first known bonebed of ornithomimids in North America, and the fourth record of an ornithomimosaur bonebed in the world. Partial skeletons representing three individuals are preserved in this assemblage, each comprising primarily portions of the posterior postcrania (pelvis, hind limbs and tail). All three individuals are morphologically similar, although one is larger in overall size. Given the stratigraphic position of the site, and the morphology of the postcrania, the preserved material represents a taxon from the clade containing Ornithomimus and Struthiomimus. Pedal ungual morphology is examined and found to be too variable to be useful in distinguishing these species taxonomically. This site provides additional evidence of gregarious behavior in ornithomimids and the first probable record of that behavior in North American forms.

  14. An ornithomimid (Dinosauria bonebed from the Late Cretaceous of Alberta, with implications for the behavior, classification, and stratigraphy of North American ornithomimids.

    Directory of Open Access Journals (Sweden)

    Thomas M Cullen

    Full Text Available Bonebeds can provide a wealth of anatomical, taphonomic, and ontogenetic information about the specimens preserved within them, and can provide evidence for inferred behavior. The material described here represents the first known bonebed of ornithomimids in North America, and the fourth record of an ornithomimosaur bonebed in the world. Partial skeletons representing three individuals are preserved in this assemblage, each comprising primarily portions of the posterior postcrania (pelvis, hind limbs and tail. All three individuals are morphologically similar, although one is larger in overall size. Given the stratigraphic position of the site, and the morphology of the postcrania, the preserved material represents a taxon from the clade containing Ornithomimus and Struthiomimus. Pedal ungual morphology is examined and found to be too variable to be useful in distinguishing these species taxonomically. This site provides additional evidence of gregarious behavior in ornithomimids and the first probable record of that behavior in North American forms.

  15. Anatomy, taphonomy, and phylogenetic implications of a new specimen of Eolambia caroljonesa (Dinosauria: Ornithopoda) from the Cedar Mountain Formation, Utah, USA

    Science.gov (United States)

    McDonald, Andrew T.; Gates, Terry A.; Zanno, Lindsay E.; Makovicky, Peter J.

    2017-01-01

    Background Eolambia caroljonesa is the most abundant dinosaur in the lower Cenomanian Mussentuchit Member of the Cedar Mountain Formation of Utah, and one of the most completely known non-hadrosaurid iguanodontians from North America. In addition to the large holotype and paratype partial skulls, copious remains of skeletally immature individuals, including three bonebeds, have been referred to E. caroljonesa. Nevertheless, aspects of the postcranial anatomy of this taxon, particularly the pelvic girdle, have remained ambiguous due to the lack of associated postcranial material of larger, more mature individuals. Methodology/Principal findings Here we describe a recently discovered associated partial postcranial skeleton of a large Eolambia caroljonesa. This specimen, FMNH PR 3847, provides new anatomical data regarding the vertebral column and pelvic girdle, supplementing previous diagnoses and descriptions of E. caroljonesa. A new phylogenetic analysis incorporating information from FMNH PR 3847 places E. caroljonesa as a basal hadrosauromorph closely related to Protohadros byrdi from the Cenomanian Woodbine Formation of Texas. Histological analysis of FMNH PR 3847 reveals that it represents a subadult individual eight to nine years of age. Taphonomic analysis indicates that FMNH PR 3847 was preserved in a crevasse splay deposit, along with an unusual abundance of small crocodylomorph material. Conclusions/Significance FMNH PR 3847 provides a wealth of new morphological data, adding to the anatomical and systematic characterization of Eolambia caroljonesa, and histological data, revealing new information on growth history in a basal hadrosauromorph. Taphonomic characterization of FMNH PR 3847 and associated vertebrate material will allow comparison with other vertebrate localities in the Mussentuchit Member of the Cedar Mountain Formation. PMID:28489871

  16. Abelisauroidea e Carcharodontosauridae (Theropoda,Dinosauria na América do Sul durante do Cretáceo. Implicações Paleogeográficas e Geocronológicas

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    Agustín Guillermo Martinelli

    2005-12-01

    Full Text Available In this contribution an up-to-date list of abelisauroid ceratosaurians and carcharodontosauridallosaurians recognized in South America is presented. Abelisauroids and carcharodontosauridsin South America show rich species diversity and a wide range of temporal and geographicaldistribution. At least eight formally described species of Abelisauroidea are recognized in Argen-tina and only one in Brazil; in contrast, only one species of Carcharodontosauridae is known forall South America. The fossil record of abelisauroids and carcharodontosaurids in South Americashows a dominance of abelisauroids in the upper late Cretaceous, while the dominance ofcarcharodontosaurids as large predators was during the Cenomanian-Turonian. Although knowl-edge of the evolution of Abelisauroidea and Carcharodontasauridae in South America, as well asin the rest of Gondwana is still far for being complete, intensive explorations in recent years haveprovided greater insight into the composition of theropod faunas in the Cretaceous of Gondwana.

  17. A new sauropod dinosaur from the Middle Jurassic of the United Kingdom.

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    Phillip L Manning

    Full Text Available A new record of a sauropodomorph dinosaur is here described from the Middle Jurassic (Aalenian Saltwick Formation of Whitby (Yorkshire, UK. A single caudal vertebra represents an early sauropodomorph and signifies the earliest recognised eusauropod dinosaur from the United Kingdom. The absence of pleurocoels and a narrow, dorsoventrally deep, but craniocaudally short centrum, suggests a primitive sauropodomorph. Distinct spinopostzygopophyseal laminae rise from the lateral margins of the postzygapophyses and pass caudally along what remains of the neural spine, a character unique to a subgroup of sauropods that includes Barapasaurus, Omeisaurus and other neosauropods and eusauropods. The lack of phylogenetically robust characters in sauropod caudal vertebrae usually makes it difficult to establish affinities, but the absence of mild procoely excludes this specimen from both Diplodocoidea and Lithostrotia. The vertebra cannot be further distinguished from those of a wide range of basal sauropods, cetiosaurids and basal macronarians. However, this plesiomorphic vertebra still signifies the earliest stratigraphic occurrence for a British sauropod dinosaur.

  18. A new sauropod dinosaur from the Middle Jurassic of the United Kingdom.

    Science.gov (United States)

    Manning, Phillip L; Egerton, Victoria M; Romano, Mike

    2015-01-01

    A new record of a sauropodomorph dinosaur is here described from the Middle Jurassic (Aalenian) Saltwick Formation of Whitby (Yorkshire), UK. A single caudal vertebra represents an early sauropodomorph and signifies the earliest recognised eusauropod dinosaur from the United Kingdom. The absence of pleurocoels and a narrow, dorsoventrally deep, but craniocaudally short centrum, suggests a primitive sauropodomorph. Distinct spinopostzygopophyseal laminae rise from the lateral margins of the postzygapophyses and pass caudally along what remains of the neural spine, a character unique to a subgroup of sauropods that includes Barapasaurus, Omeisaurus and other neosauropods and eusauropods. The lack of phylogenetically robust characters in sauropod caudal vertebrae usually makes it difficult to establish affinities, but the absence of mild procoely excludes this specimen from both Diplodocoidea and Lithostrotia. The vertebra cannot be further distinguished from those of a wide range of basal sauropods, cetiosaurids and basal macronarians. However, this plesiomorphic vertebra still signifies the earliest stratigraphic occurrence for a British sauropod dinosaur.

  19. Novel insight into the origin of the growth dynamics of sauropod dinosaurs.

    Science.gov (United States)

    Cerda, Ignacio Alejandro; Chinsamy, Anusuya; Pol, Diego; Apaldetti, Cecilia; Otero, Alejandro; Powell, Jaime Eduardo; Martínez, Ricardo Nestor

    2017-01-01

    Sauropod dinosaurs include the largest terrestrial animals and are considered to have uninterrupted rapid rates of growth, which differs from their more basal relatives, which have a slower cyclical growth. Here we examine the bone microstructure of several sauropodomorph dinosaurs, including basal taxa, as well as the more derived sauropods. Although our results agree that the plesiomorphic condition for Sauropodomorpha is cyclical growth dynamics, we found that the hypothesized dichotomy between the growth patterns of basal and more derived sauropodomorphs is not supported. Here, we show that sauropod-like growth dynamics of uninterrupted rapid growth also occurred in some basal sauropodomorphs, and that some basal sauropods retained the plesiomorphic cyclical growth patterns. Among the sauropodomorpha it appears that the basal taxa exploited different growth strategies, but the more derived Eusauropoda successfully utilized rapid, uninterrupted growth strategies.

  20. The oldest dinosaur? A Middle Triassic dinosauriform from Tanzania.

    Science.gov (United States)

    Nesbitt, Sterling J; Barrett, Paul M; Werning, Sarah; Sidor, Christian A; Charig, Alan J

    2013-02-23

    The rise of dinosaurs was a major event in vertebrate history, but the timing of the origin and early diversification of the group remain poorly constrained. Here, we describe Nyasasaurus parringtoni gen. et sp. nov., which is identified as either the earliest known member of, or the sister-taxon to, Dinosauria. Nyasasaurus possesses a unique combination of dinosaur character states and an elevated growth rate similar to that of definitive early dinosaurs. It demonstrates that the initial dinosaur radiation occurred over a longer timescale than previously thought (possibly 15 Myr earlier), and that dinosaurs and their immediate relatives are better understood as part of a larger Middle Triassic archosauriform radiation. The African provenance of Nyasasaurus supports a southern Pangaean origin for Dinosauria.

  1. A New Leptoceratopsid (Ornithischia, Ceratopsia) with a Unique Ischium from the Upper Cretaceous of Shandong Province, China

    OpenAIRE

    Yiming He; Makovicky, Peter J.; Kebai Wang; Shuqing Chen; Corwin Sullivan; Fenglu Han; Xing Xu

    2015-01-01

    The partial skeleton of a leptoceratopsid dinosaur, Ischioceratops zhuchengensis gen. et sp. nov., was excavated from the bone-beds of the Upper Cretaceous Wangshi Group of Zhucheng, Shandong Province, China. This fossil represents the second leptoceratopsid dinosaur specimen recovered from the Kugou locality, a highly productive site in Zhucheng. The ischium of the new taxon is morphologically unique among known Dinosauria, flaring gradually to form an obturator process in its middle portion...

  2. Mesozoic plants and dinosaur herbivory

    OpenAIRE

    Sander, P. M.; Gee, C T; Hummel, J; Clauss, Marcus

    2010-01-01

    For most of their existence, herbivorous dinosaurs fed on a gymnospermdominated flora. Starting from a simple reptilian herbivory, ornithischian dinosaurs evolved complex chewing dentitions and mechanisms, while sauropodomorph dinosaurs retained the primitive condition of not chewing. Some advanced theropod dinosaurs evolved a bird-type herbivory with a toothless beak and a gastric mill. Dinosaur digestive tract remains, coprolites, and other trace fossils offer little evidence for dinosaur f...

  3. Asociacion faunistica de vertebrados mesozoicos de la localidad de Galve (Teruel

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    Sánchez Hemández, B.

    2002-12-01

    Full Text Available Sediments of Tithonian-Barremian of Iberian Basin in the surroundings of Galve (Teniel, Spain have a high content of vertebrate's remains. These ones have been studied since s. XX until today by different scientists. More than ninety taxons have been mentioned in these papers, distributed in Hybodontiformes, Squalomorpha, Batoidea, Rajiforms, Amphibia, Reptilia (Chelonia, Sauria, Crocodylia, Pterosauria, Ornithischia, Saurischia and Marnmalia.Los sedimentos del Tithónico-Barremiense de la Cuenca Ibérica aflorantes en los alrededores de la localidad de Galve (Teniel, son particularmente ricos en restos de vertebrados mesozoicos. Estos han sido estudiados por diferentes autores, desde principios del siglo xx hasta la actualidad. El objetivo del presente artículo es recopilar los distintos taxones que han sido citados para esta área, a lo largo del tiempo, recogiéndose más de noventa taxones distribuidos entre Hybodontiformes, Squalomorpha, Batoidea, Rajiformes, Amphibia, Reptilia (Testudines, Sauria, Crocodilia, Pterosauria, Ornithischia, Saurischia y Mammalia.

  4. Body temperatures in dinosaurs: what can growth curves tell us?

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    Eva Maria Griebeler

    Full Text Available To estimate the body temperature (BT of seven dinosaurs Gillooly, Alleen, and Charnov (2006 used an equation that predicts BT from the body mass and maximum growth rate (MGR with the latter preserved in ontogenetic growth trajectories (BT-equation. The results of these authors evidence inertial homeothermy in Dinosauria and suggest that, due to overheating, the maximum body size in Dinosauria was ultimately limited by BT. In this paper, I revisit this hypothesis of Gillooly, Alleen, and Charnov (2006. I first studied whether BTs derived from the BT-equation of today's crocodiles, birds and mammals are consistent with core temperatures of animals. Second, I applied the BT-equation to a larger number of dinosaurs than Gillooly, Alleen, and Charnov (2006 did. In particular, I estimated BT of Archaeopteryx (from two MGRs, ornithischians (two, theropods (three, prosauropods (three, and sauropods (nine. For extant species, the BT value estimated from the BT-equation was a poor estimate of an animal's core temperature. For birds, BT was always strongly overestimated and for crocodiles underestimated; for mammals the accuracy of BT was moderate. I argue that taxon-specific differences in the scaling of MGR (intercept and exponent of the regression line, log-log-transformed and in the parameterization of the Arrhenius model both used in the BT-equation as well as ecological and evolutionary adaptations of species cause these inaccuracies. Irrespective of the found inaccuracy of BTs estimated from the BT-equation and contrary to the results of Gillooly, Alleen, and Charnov (2006 I found no increase in BT with increasing body mass across all dinosaurs (Sauropodomorpha, Sauropoda studied. This observation questions that, due to overheating, the maximum size in Dinosauria was ultimately limited by BT. However, the general high inaccuracy of dinosaurian BTs derived from the BT-equation makes a reliable test of whether body size in dinosaurs was ultimately

  5. Body temperatures in dinosaurs: what can growth curves tell us?

    Science.gov (United States)

    Griebeler, Eva Maria

    2013-01-01

    To estimate the body temperature (BT) of seven dinosaurs Gillooly, Alleen, and Charnov (2006) used an equation that predicts BT from the body mass and maximum growth rate (MGR) with the latter preserved in ontogenetic growth trajectories (BT-equation). The results of these authors evidence inertial homeothermy in Dinosauria and suggest that, due to overheating, the maximum body size in Dinosauria was ultimately limited by BT. In this paper, I revisit this hypothesis of Gillooly, Alleen, and Charnov (2006). I first studied whether BTs derived from the BT-equation of today's crocodiles, birds and mammals are consistent with core temperatures of animals. Second, I applied the BT-equation to a larger number of dinosaurs than Gillooly, Alleen, and Charnov (2006) did. In particular, I estimated BT of Archaeopteryx (from two MGRs), ornithischians (two), theropods (three), prosauropods (three), and sauropods (nine). For extant species, the BT value estimated from the BT-equation was a poor estimate of an animal's core temperature. For birds, BT was always strongly overestimated and for crocodiles underestimated; for mammals the accuracy of BT was moderate. I argue that taxon-specific differences in the scaling of MGR (intercept and exponent of the regression line, log-log-transformed) and in the parameterization of the Arrhenius model both used in the BT-equation as well as ecological and evolutionary adaptations of species cause these inaccuracies. Irrespective of the found inaccuracy of BTs estimated from the BT-equation and contrary to the results of Gillooly, Alleen, and Charnov (2006) I found no increase in BT with increasing body mass across all dinosaurs (Sauropodomorpha, Sauropoda) studied. This observation questions that, due to overheating, the maximum size in Dinosauria was ultimately limited by BT. However, the general high inaccuracy of dinosaurian BTs derived from the BT-equation makes a reliable test of whether body size in dinosaurs was ultimately limited

  6. Découverte d'un gisement à vertébrés dans le Maastrichtien supérieur des Petites-Pyrénées

    Science.gov (United States)

    Laurent, Yves; Cavin, Lionel; Bilotte, Michel

    1999-06-01

    A new Late Maastrichtian locality from the Petites-Pyrénées has yielded an important vertebrate fauna. It includes Chondrichthyes (undetermined neoselachian), Osteichthyes (Lepisosteidae, Phyllodontinae, Sparidae?), Chelonia (Pleurodira), Crocodylia, and Dinosauria (Theropoda, Hadrosauridae, Nodosauridae). It is the first mention of a Cretaceous phyllodontine and the first mention of an ankylosaur in the French Late Maastrichtian. Lestaillats is the richest Late Maastrichtian locality in southern France because of the occurrence of both a microfauna and macrovertebrates. It offers new perspectives for the knowledge of the diversity and the evolution of the European vertebrate assemblages in the Latest Cretaceous.

  7. Incubation times of dinosaur eggs via embryonic metabolism

    Science.gov (United States)

    Lee, Scott A.

    2016-08-01

    The incubation times for the eggs of 21 dinosaurs are determined from an estimate of their embyronic metabolic rate and the mass of the hatchlings via a mass growth model based on conservation of energy. Embryos in extant birds and crocodiles are studied in order to determine the best model for embryonic metabolism and growth. These results are used to develop a theoretical model that predicts the incubation times of an egg. This model is applied to dinosaur eggs and provides a unique window into dinosaur reproduction. The dinosaurs studied come from both Saurischia and Ornithischia. The incubation times vary from about 28 days for Archaeopteryx lithographica to about 76 days for Alamosaurus sanjuanensis.

  8. New insights into non-avian dinosaur reproduction and their evolutionary and ecological implications: linking fossil evidence to allometries of extant close relatives.

    Science.gov (United States)

    Werner, Jan; Griebeler, Eva Maria

    2013-01-01

    It has been hypothesized that a high reproductive output contributes to the unique gigantism in large dinosaur taxa. In order to infer more information on dinosaur reproduction, we established allometries between body mass and different reproductive traits (egg mass, clutch mass, annual clutch mass) for extant phylogenetic brackets (birds, crocodiles and tortoises) of extinct non-avian dinosaurs. Allometries were applied to nine non-avian dinosaur taxa (theropods, hadrosaurs, and sauropodomorphs) for which fossil estimates on relevant traits are currently available. We found that the reproductive traits of most dinosaurs conformed to similar-sized or scaled-up extant reptiles or birds. The reproductive traits of theropods, which are considered more bird-like, were indeed consistent with birds, while the traits of sauropodomorphs conformed better to reptiles. Reproductive traits of hadrosaurs corresponded to both reptiles and birds. Excluding Massospondyluscarinatus, all dinosaurs studied had an intermediary egg to body mass relationship to reptiles and birds. In contrast, dinosaur clutch masses fitted with either the masses predicted from allometries of birds (theropods) or to the masses of reptiles (all other taxa). Theropods studied had probably one clutch per year. For sauropodomorphs and hadrosaurs, more than one clutch per year was predicted. Contrary to current hypotheses, large dinosaurs did not have exceptionally high annual egg numbers (AEN). Independent of the extant model, the estimated dinosaur AEN did not exceed 850 eggs (75,000 kg sauropod) for any of the taxa studied. This estimated maximum is probably an overestimation due to unrealistic assumptions. According to most AEN estimations, the dinosaurs studied laid less than 200 eggs per year. Only some AEN estimates obtained for medium to large sized sauropods were higher (200-400 eggs). Our results provide new (testable) hypotheses, especially for reproductive traits that are insufficiently documented

  9. Embryology of Early Jurassic dinosaur from China with evidence of preserved organic remains.

    Science.gov (United States)

    Reisz, Robert R; Huang, Timothy D; Roberts, Eric M; Peng, ShinRung; Sullivan, Corwin; Stein, Koen; LeBlanc, Aaron R H; Shieh, DarBin; Chang, RongSeng; Chiang, ChengCheng; Yang, Chuanwei; Zhong, Shiming

    2013-04-11

    Fossil dinosaur embryos are surprisingly rare, being almost entirely restricted to Upper Cretaceous strata that record the late stages of non-avian dinosaur evolution. Notable exceptions are the oldest known embryos from the Early Jurassic South African sauropodomorph Massospondylus and Late Jurassic embryos of a theropod from Portugal. The fact that dinosaur embryos are rare and typically enclosed in eggshells limits their availability for tissue and cellular level investigations of development. Consequently, little is known about growth patterns in dinosaur embryos, even though post-hatching ontogeny has been studied in several taxa. Here we report the discovery of an embryonic dinosaur bone bed from the Lower Jurassic of China, the oldest such occurrence in the fossil record. The embryos are similar in geological age to those of Massospondylus and are also assignable to a sauropodomorph dinosaur, probably Lufengosaurus. The preservation of numerous disarticulated skeletal elements and eggshells in this monotaxic bone bed, representing different stages of incubation and therefore derived from different nests, provides opportunities for new investigations of dinosaur embryology in a clade noted for gigantism. For example, comparisons among embryonic femora of different sizes and developmental stages reveal a consistently rapid rate of growth throughout development, possibly indicating that short incubation times were characteristic of sauropodomorphs. In addition, asymmetric radial growth of the femoral shaft and rapid expansion of the fourth trochanter suggest that embryonic muscle activation played an important role in the pre-hatching ontogeny of these dinosaurs. This discovery also provides the oldest evidence of in situ preservation of complex organic remains in a terrestrial vertebrate.

  10. New insights into non-avian dinosaur reproduction and their evolutionary and ecological implications: linking fossil evidence to allometries of extant close relatives.

    Directory of Open Access Journals (Sweden)

    Jan Werner

    Full Text Available It has been hypothesized that a high reproductive output contributes to the unique gigantism in large dinosaur taxa. In order to infer more information on dinosaur reproduction, we established allometries between body mass and different reproductive traits (egg mass, clutch mass, annual clutch mass for extant phylogenetic brackets (birds, crocodiles and tortoises of extinct non-avian dinosaurs. Allometries were applied to nine non-avian dinosaur taxa (theropods, hadrosaurs, and sauropodomorphs for which fossil estimates on relevant traits are currently available. We found that the reproductive traits of most dinosaurs conformed to similar-sized or scaled-up extant reptiles or birds. The reproductive traits of theropods, which are considered more bird-like, were indeed consistent with birds, while the traits of sauropodomorphs conformed better to reptiles. Reproductive traits of hadrosaurs corresponded to both reptiles and birds. Excluding Massospondyluscarinatus, all dinosaurs studied had an intermediary egg to body mass relationship to reptiles and birds. In contrast, dinosaur clutch masses fitted with either the masses predicted from allometries of birds (theropods or to the masses of reptiles (all other taxa. Theropods studied had probably one clutch per year. For sauropodomorphs and hadrosaurs, more than one clutch per year was predicted. Contrary to current hypotheses, large dinosaurs did not have exceptionally high annual egg numbers (AEN. Independent of the extant model, the estimated dinosaur AEN did not exceed 850 eggs (75,000 kg sauropod for any of the taxa studied. This estimated maximum is probably an overestimation due to unrealistic assumptions. According to most AEN estimations, the dinosaurs studied laid less than 200 eggs per year. Only some AEN estimates obtained for medium to large sized sauropods were higher (200-400 eggs. Our results provide new (testable hypotheses, especially for reproductive traits that are insufficiently

  11. New Insights into Non-Avian Dinosaur Reproduction and Their Evolutionary and Ecological Implications: Linking Fossil Evidence to Allometries of Extant Close Relatives

    Science.gov (United States)

    Werner, Jan; Griebeler, Eva Maria

    2013-01-01

    It has been hypothesized that a high reproductive output contributes to the unique gigantism in large dinosaur taxa. In order to infer more information on dinosaur reproduction, we established allometries between body mass and different reproductive traits (egg mass, clutch mass, annual clutch mass) for extant phylogenetic brackets (birds, crocodiles and tortoises) of extinct non-avian dinosaurs. Allometries were applied to nine non-avian dinosaur taxa (theropods, hadrosaurs, and sauropodomorphs) for which fossil estimates on relevant traits are currently available. We found that the reproductive traits of most dinosaurs conformed to similar-sized or scaled-up extant reptiles or birds. The reproductive traits of theropods, which are considered more bird-like, were indeed consistent with birds, while the traits of sauropodomorphs conformed better to reptiles. Reproductive traits of hadrosaurs corresponded to both reptiles and birds. Excluding Massospondyluscarinatus, all dinosaurs studied had an intermediary egg to body mass relationship to reptiles and birds. In contrast, dinosaur clutch masses fitted with either the masses predicted from allometries of birds (theropods) or to the masses of reptiles (all other taxa). Theropods studied had probably one clutch per year. For sauropodomorphs and hadrosaurs, more than one clutch per year was predicted. Contrary to current hypotheses, large dinosaurs did not have exceptionally high annual egg numbers (AEN). Independent of the extant model, the estimated dinosaur AEN did not exceed 850 eggs (75,000 kg sauropod) for any of the taxa studied. This estimated maximum is probably an overestimation due to unrealistic assumptions. According to most AEN estimations, the dinosaurs studied laid less than 200 eggs per year. Only some AEN estimates obtained for medium to large sized sauropods were higher (200-400 eggs). Our results provide new (testable) hypotheses, especially for reproductive traits that are insufficiently documented

  12. A new basal sauropodiform dinosaur from the Lower Jurassic of Yunnan Province, China.

    Science.gov (United States)

    Wang, Ya-Ming; You, Hai-Lu; Wang, Tao

    2017-02-16

    The Lufeng Formation in Lufeng Basin of Yunnan Province, southwestern China preserves one of the richest terrestrial Lower Jurassic vertebrate faunas globally, especially for its basal sauropodomorphs, such as Lufengosaurus and Yunnanosaurus. Here we report a new taxon, Xingxiulong chengi gen. et sp. nov. represented by three partial skeletons with overlapping elements. Xingxiulong possesses a number of autapomorphies, such as transversely expanded plate-like summit on top of the neural spine of posterior dorsal vertebrae, four sacral vertebrae, robust scapula, and elongated pubic plate approximately 40% of the total length of the pubis. Phylogenetic analysis resolves Xingxiulong as a basal member of Sauropodiformes, and together with another two Lufeng basal sauropodiforms Jingshanosaurus and Yunnanosaurus, they represent the basalmost lineages of this clade, indicating its Asian origin. Although being relatively primitive, Xingxiulong displays some derived features normally occurred in advanced sauropodiforms including sauropods, such as a four sacral-sacrum, a robust scapula, and a pubis with elongated pubic plate. The discovery of Xingxiulong increases the diversity of basal sauropodomorphs from the Lufeng Formation and indicates a more complicated scenario in the early evolution of sauropodiforms.

  13. A new basal sauropodiform dinosaur from the Lower Jurassic of Yunnan Province, China

    Science.gov (United States)

    Wang, Ya-Ming; You, Hai-Lu; Wang, Tao

    2017-02-01

    The Lufeng Formation in Lufeng Basin of Yunnan Province, southwestern China preserves one of the richest terrestrial Lower Jurassic vertebrate faunas globally, especially for its basal sauropodomorphs, such as Lufengosaurus and Yunnanosaurus. Here we report a new taxon, Xingxiulong chengi gen. et sp. nov. represented by three partial skeletons with overlapping elements. Xingxiulong possesses a number of autapomorphies, such as transversely expanded plate-like summit on top of the neural spine of posterior dorsal vertebrae, four sacral vertebrae, robust scapula, and elongated pubic plate approximately 40% of the total length of the pubis. Phylogenetic analysis resolves Xingxiulong as a basal member of Sauropodiformes, and together with another two Lufeng basal sauropodiforms Jingshanosaurus and Yunnanosaurus, they represent the basalmost lineages of this clade, indicating its Asian origin. Although being relatively primitive, Xingxiulong displays some derived features normally occurred in advanced sauropodiforms including sauropods, such as a four sacral-sacrum, a robust scapula, and a pubis with elongated pubic plate. The discovery of Xingxiulong increases the diversity of basal sauropodomorphs from the Lufeng Formation and indicates a more complicated scenario in the early evolution of sauropodiforms.

  14. Endocast of the Late Triassic (Carnian) dinosaur Saturnalia tupiniquim: implications for the evolution of brain tissue in Sauropodomorpha.

    Science.gov (United States)

    Bronzati, Mario; Rauhut, Oliver W M; Bittencourt, Jonathas S; Langer, Max C

    2017-09-20

    The evolutionary history of dinosaurs might date back to the first stages of the Triassic (c. 250-240 Ma), but the oldest unequivocal records of the group come from Late Triassic (Carnian - c. 230 Ma) rocks of South America. Here, we present the first braincase endocast of a Carnian dinosaur, the sauropodomorph Saturnalia tupiniquim, and provide new data regarding the evolution of the floccular and parafloccular lobe of the cerebellum (FFL), which has been extensively discussed in the field of palaeoneurology. Previous studies proposed that the development of a permanent quadrupedal stance was one of the factors leading to the volume reduction of the FFL of sauropods. However, based on the new data for S. tupiniquim we identified a first moment of FFL volume reduction in non-sauropodan Sauropodomorpha, preceding the acquisition of a fully quadrupedal stance. Analysing variations in FFL volume alongside other morphological changes in the group, we suggest that this reduction is potentially related to the adoption of a more restricted herbivore diet. In this context, the FFL of sauropods might represent a vestigial trait, retained in a reduced version from the bipedal and predatory early sauropodomorphs.

  15. Preliminary analysis of osteocyte lacunar density in long bones of tetrapods: all measures are bigger in sauropod dinosaurs.

    Directory of Open Access Journals (Sweden)

    Koen W H Stein

    Full Text Available Osteocytes harbour much potential for paleobiological studies. Synchrotron radiation and spectroscopic analyses are providing fascinating data on osteocyte density, size and orientation in fossil taxa. However, such studies may be costly and time consuming. Here we describe an uncomplicated and inexpensive method to measure osteocyte lacunar densities in bone thin sections. We report on cell lacunar densities in the long bones of various extant and extinct tetrapods, with a focus on sauropodomorph dinosaurs, and how lacunar densities can help us understand bone formation rates in the iconic sauropod dinosaurs. Ordinary least square and phylogenetic generalized least square regressions suggest that sauropodomorphs have lacunar densities higher than scaled up or comparably sized mammals. We also found normal mammalian-like osteocyte densities for the extinct bovid Myotragus, questioning its crocodilian-like physiology. When accounting for body mass effects and phylogeny, growth rates are a main factor determining the density of the lacunocanalicular network. However, functional aspects most likely play an important role as well. Observed differences in cell strategies between mammals and dinosaurs likely illustrate the convergent nature of fast growing bone tissues in these groups.

  16. Preliminary analysis of osteocyte lacunar density in long bones of tetrapods: all measures are bigger in sauropod dinosaurs.

    Science.gov (United States)

    Stein, Koen W H; Werner, Jan

    2013-01-01

    Osteocytes harbour much potential for paleobiological studies. Synchrotron radiation and spectroscopic analyses are providing fascinating data on osteocyte density, size and orientation in fossil taxa. However, such studies may be costly and time consuming. Here we describe an uncomplicated and inexpensive method to measure osteocyte lacunar densities in bone thin sections. We report on cell lacunar densities in the long bones of various extant and extinct tetrapods, with a focus on sauropodomorph dinosaurs, and how lacunar densities can help us understand bone formation rates in the iconic sauropod dinosaurs. Ordinary least square and phylogenetic generalized least square regressions suggest that sauropodomorphs have lacunar densities higher than scaled up or comparably sized mammals. We also found normal mammalian-like osteocyte densities for the extinct bovid Myotragus, questioning its crocodilian-like physiology. When accounting for body mass effects and phylogeny, growth rates are a main factor determining the density of the lacunocanalicular network. However, functional aspects most likely play an important role as well. Observed differences in cell strategies between mammals and dinosaurs likely illustrate the convergent nature of fast growing bone tissues in these groups.

  17. A New Leptoceratopsid (Ornithischia, Ceratopsia) with a Unique Ischium from the Upper Cretaceous of Shandong Province, China.

    Science.gov (United States)

    He, Yiming; Makovicky, Peter J; Wang, Kebai; Chen, Shuqing; Sullivan, Corwin; Han, Fenglu; Xu, Xing

    2015-01-01

    The partial skeleton of a leptoceratopsid dinosaur, Ischioceratops zhuchengensis gen. et sp. nov., was excavated from the bone-beds of the Upper Cretaceous Wangshi Group of Zhucheng, Shandong Province, China. This fossil represents the second leptoceratopsid dinosaur specimen recovered from the Kugou locality, a highly productive site in Zhucheng. The ischium of the new taxon is morphologically unique among known Dinosauria, flaring gradually to form an obturator process in its middle portion and resembling the shaft of a recurve bow. An elliptical fenestra perforates the obturator process, and the distal end of the shaft forms an axehead-shaped expansion. The discovery of Ischioceratops increases the known taxonomic diversity and morphological disparity of the Leptoceratopsidae.

  18. A New Leptoceratopsid (Ornithischia, Ceratopsia with a Unique Ischium from the Upper Cretaceous of Shandong Province, China.

    Directory of Open Access Journals (Sweden)

    Yiming He

    Full Text Available The partial skeleton of a leptoceratopsid dinosaur, Ischioceratops zhuchengensis gen. et sp. nov., was excavated from the bone-beds of the Upper Cretaceous Wangshi Group of Zhucheng, Shandong Province, China. This fossil represents the second leptoceratopsid dinosaur specimen recovered from the Kugou locality, a highly productive site in Zhucheng. The ischium of the new taxon is morphologically unique among known Dinosauria, flaring gradually to form an obturator process in its middle portion and resembling the shaft of a recurve bow. An elliptical fenestra perforates the obturator process, and the distal end of the shaft forms an axehead-shaped expansion. The discovery of Ischioceratops increases the known taxonomic diversity and morphological disparity of the Leptoceratopsidae.

  19. A REEXAMINATION OF FOUR PROLACERTIFORMS WITH IMPLICATIONS FOR PTEROSAUR PHYLOGENESIS

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    DAVID PETERS

    2000-11-01

    Full Text Available Traditionally, pterosaurs have been included within the Archosauriformes and many contemporary workers consider the Pterosauria the sister group to Lagosuchus, Scleromochlus and the Dinosauria. New analyses cast doubts on those relationships because nearly all presumed archosauriform or ornithodire "synapomorpies" are either not present within the Pterosauria or are also present within certain prolacertiform taxa. Recent examinations of the holotypes of Cosesaurus aviceps, Longisquama insignis and Sharovipteryx mirabilis suggest that many characters may be interpreted differently than previously reported. Results of several subsequent cladistic analyses suggests that these "enigmatic" prolacertiforms, along with the newly described Langobardisaurus, are sister taxa to the Pterosauria, based on a suite of newly identified synapomorphies. 

  20. Paleobiology of Herbivorous Dinosaurs

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    Barrett, Paul M.

    2014-05-01

    Herbivorous dinosaurs were abundant, species-rich components of Late Triassic-Cretaceous terrestrial ecosystems. Obligate high-fiber herbivory evolved independently on several occasions within Dinosauria, through the intermediary step of omnivory. Anatomical character complexes associated with this diet exhibit high levels of convergence and morphological disparity, and may have evolved by correlated progression. Dinosaur faunas changed markedly during the Mesozoic, from early faunas dominated by taxa with simple, uniform feeding mechanics to Cretaceous biomes including diverse sophisticated sympatric herbivores; the environmental and biological drivers causing these changes remain unclear. Isotopic, taphonomic, and anatomical evidence implies that niche partitioning reduced competition between sympatric herbivores, via morphological differentiation, dietary preferences, and habitat selection. Large body size in dinosaur herbivores is associated with low plant productivity, and gave these animals prominent roles as ecosystem engineers. Although dinosaur herbivores lived through several major events in floral evolution, there is currently no evidence for plant-dinosaur coevolutionary interactions.

  1. Cross-species transmission and emergence of novel viruses from birds.

    Science.gov (United States)

    Chan, Jasper Fuk-Woo; To, Kelvin Kai-Wang; Chen, Honglin; Yuen, Kwok-Yung

    2015-02-01

    Birds, the only living member of the Dinosauria clade, are flying warm-blooded vertebrates displaying high species biodiversity, roosting and migratory behavior, and a unique adaptive immune system. Birds provide the natural reservoir for numerous viral species and therefore gene source for evolution, emergence and dissemination of novel viruses. The intrusions of human into natural habitats of wild birds, the domestication of wild birds as pets or racing birds, and the increasing poultry consumption by human have facilitated avian viruses to cross species barriers to cause zoonosis. Recently, a novel adenovirus was exclusively found in birds causing an outbreak of Chlamydophila psittaci infection among birds and humans. Instead of being the primary cause of an outbreak by jumping directly from bird to human, a novel avian virus can be an augmenter of another zoonotic agent causing the outbreak. A comprehensive avian virome will improve our understanding of birds' evolutionary dynamics. Copyright © 2015 Elsevier B.V. All rights reserved.

  2. Dinosaur Reproduction and Parenting

    Science.gov (United States)

    Horner, John R.

    Non-avian dinosaur reproductive and parenting behaviors were mostly similar to those of extant archosaurs. Non-avian dinosaurs were probably sexually dimorphic and some may have engaged in hierarchical rituals. Non-avian coelurosaurs (e.g. Troodontidae, Oviraptorosauria) had two active oviducts, each of which produced single eggs on a daily or greater time scale. The eggs of non-coelurosaurian dinosaurs (e.g. Ornithischia, Sauropoda) were incubated in soils, whereas the eggs of non-avian coelurosaurs (e.g. Troodon, Oviraptor) were incubated with a combination of soil and direct parental contact. Parental attention to the young was variable, ranging from protection from predators to possible parental feeding of nest-bound hatchlings. Semi-altricial hadrosaur hatchlings exited their respective nests near the time of their first linear doubling. Some reproductive behaviors, once thought exclusive to Aves, arose first in non-avian dinosaurs. The success of the Dinosauria may be related to reproductive strategies.

  3. The Evolution and Extinction of the Dinosaurs

    Science.gov (United States)

    Fastovsky, David E.; Weishampel, David B.

    2005-02-01

    Written for non-specialists, this detailed survey of dinosaur origins, diversity, and extinction is designed as a series of successive essays covering important and timely topics in dinosaur paleobiology, such as "warm-bloodedness," birds as living dinosaurs, the new, non-flying feathered dinosaurs, dinosaur functional morphology, and cladistic methods in systematics. Its explicitly phylogenetic approach to the group is that taken by dinosaur specialists. The book is not an edited compilation of the works of many individuals, but a unique, cohesive perspective on Dinosauria. Lavishly illustrated with hundreds of new, specially commissioned illustrations by John Sibbick, world-famous illustrator of dinosaurs, the volume includes multi-page drawings as well as sketches and diagrams. First edition Hb (1996): 0-521-44496-9 David E. Fastovsky is Professor of Geosciences at the University of Rhode Island. Fastovsky, the author of numerous scientific publications dealing with Mesozoic vertebrate faunas and their ancient environments, is also scientific co-Editor of Geology. He has undertaken extensive fieldwork studying dinosaurs and their environments in Montana, North Dakota, Arizona, Mexico, and Mongolia. David B. Weishampel is a professor at the Center for Functional Anatomy and Evolution at Johns Hopkins University, School of Medicine. Weishampel is best known for discovering, researching, and naming several rare European dinosaur species. During the 1980s Weishampel gained fame for his work with American paleontologist Jack Horner and later named the famous plant-eating, egg-laying Orodromeus, Horner. Now, a decade after his pioneering studies with Horner, Weishampel is most widely known for his current work on the Romanian dinosaur fauna. He is the author and co-author of many titles, including The Dinosaur Papers, 1676-1906 (Norton, 2003); The Dinosauria, (University of California, 1990); and Dinosaurs of the East Coast, (Johns Hopkins University Press, 1996).

  4. The braincase of the basal sauropod dinosaur Spinophorosaurus and 3D reconstructions of the cranial endocast and inner ear.

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    Fabien Knoll

    Full Text Available BACKGROUND: Sauropod dinosaurs were the largest animals ever to walk on land, and, as a result, the evolution of their remarkable adaptations has been of great interest. The braincase is of particular interest because it houses the brain and inner ear. However, only a few studies of these structures in sauropods are available to date. Because of the phylogenetic position of Spinophorosaurus nigerensis as a basal eusauropod, the braincase has the potential to provide key evidence on the evolutionary transition relative to other dinosaurs. METHODOLOGY/PRINCIPAL FINDINGS: The only known braincase of Spinophorosaurus ('Argiles de l'Irhazer', Irhazer Group; Agadez region, Niger differs significantly from those of the Jurassic sauropods examined, except potentially for Atlasaurus imelakei (Tilougguit Formation, Morocco. The basisphenoids of Spinophorosaurus and Atlasaurus bear basipterygoid processes that are comparable in being directed strongly caudally. The Spinophorosaurus specimen was CT scanned, and 3D renderings of the cranial endocast and inner-ear system were generated. The endocast resembles that of most other sauropods in having well-marked pontine and cerebral flexures, a large and oblong pituitary fossa, and in having the brain structure obscured by the former existence of relatively thick meninges and dural venous sinuses. The labyrinth is characterized by long and proportionally slender semicircular canals. This condition recalls, in particular, that of the basal non-sauropod sauropodomorph Massospondylus and the basal titanosauriform Giraffatitan. CONCLUSIONS/SIGNIFICANCE: Spinophorosaurus has a moderately derived paleoneuroanatomical pattern. In contrast to what might be expected early within a lineage leading to plant-eating graviportal quadrupeds, Spinophorosaurus and other (but not all sauropodomorphs show no reduction of the vestibular apparatus of the inner ear. This character-state is possibly a primitive retention in

  5. Oology and the evolution of thermophysiology in saurischian dinosaurs: homeotherm and endotherm deinonychosaurians?

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    Gerald Grellet-Tinner

    2006-01-01

    Full Text Available The origin of avian endothermy is a long-held question the answer of which cannot be provided by first level observations. Oological and reproductive characters have collectively provided a new source of data useful for phylogenetic analyses and paleobiological inferences. In addition, the observations of reproductive and oological evolutionary trends in saurischian dinosaurs lead to the interpretation that not only, the thermophysiology of these dinosaurs progressively became more avian-like but after re-examination allows to infer that deinonychosaurians represented here by three troodontids and one dromaeosaurid might already have developed an avian-like endothermy, thus predating the rise of avians. These results based on reproductive traits are independently corroborated by the discoveries of troodontid dinosaurs 1 in high latitudes, 2 covered with feathers in Chinese Lagerstätten, and recently 3 fossilized in a death pose identical to an avian sleeping posture.A origem da endotermia nas aves é uma questão há muito discutida e sua resposta não pode ser encontrada através de observações superficiais. Caracteres oológicos e reprodutivos surgiram como uma nova fonte de dados relevantes tanto para análises filogenéticas quanto para inferências paleobiológicas dos dinossauros Saurischia. Além disso, as observações das tendências evolutivas reprodutivas e oológicas nos dinossauros Saurischia nos levam a inferir que não apenas, como anteriormente a termofisiologia deste grupo de dinossauros tornou-se progressivamente ornítica, mas um posterior reexame nos permitiu concluir que os deinonicossauros, representados aqui por dois troodontídeos e um dromeossaurídeo, provavelmente já haviam desenvolvido uma endotermia semelhante a das aves, anterior, portanto, ao seu surgimento. Estes resultados baseados em características reprodutivas são independentemente corroborados pela descoberta dos dinossauros troodontídeos 1 em altas

  6. Preservational bias controls the fossil record of pterosaurs.

    Science.gov (United States)

    Dean, Christopher D; Mannion, Philip D; Butler, Richard J

    2016-01-14

    Pterosaurs, a Mesozoic group of flying archosaurs, have become a focal point for debates pertaining to the impact of sampling biases on our reading of the fossil record, as well as the utility of sampling proxies in palaeodiversity reconstructions. The completeness of the pterosaur fossil specimens themselves potentially provides additional information that is not captured in existing sampling proxies, and might shed new light on the group's evolutionary history. Here we assess the quality of the pterosaur fossil record via a character completeness metric based on the number of phylogenetic characters that can be scored for all known skeletons of 172 valid species, with averaged completeness values calculated for each geological stage. The fossil record of pterosaurs is observed to be strongly influenced by the occurrence and distribution of Lagerstätten. Peaks in completeness correlate with Lagerstätten deposits, and a recovered correlation between completeness and observed diversity is rendered non-significant when Lagerstätten species are excluded. Intervals previously regarded as potential extinction events are shown to lack Lagerstätten and exhibit low completeness values: as such, the apparent low diversity in these intervals might be at least partly the result of poor fossil record quality. A positive correlation between temporal patterns in completeness of Cretaceous pterosaurs and birds further demonstrates the prominent role that Lagerstätten deposits have on the preservation of smaller bodied organisms, contrasting with a lack of correlation with the completeness of large-bodied sauropodomorphs. However, we unexpectedly find a strong correlation between sauropodomorph and pterosaur completeness within the Triassic-Jurassic, but not the Cretaceous, potentially relating to a shared shift in environmental preference and thus preservation style through time. This study highlights the importance of understanding the relationship between various

  7. Evolution of high tooth replacement rates in sauropod dinosaurs.

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    Michael D D'Emic

    Full Text Available BACKGROUND: Tooth replacement rate can be calculated in extinct animals by counting incremental lines of deposition in tooth dentin. Calculating this rate in several taxa allows for the study of the evolution of tooth replacement rate. Sauropod dinosaurs, the largest terrestrial animals that ever evolved, exhibited a diversity of tooth sizes and shapes, but little is known about their tooth replacement rates. METHODOLOGY/PRINCIPAL FINDINGS: We present tooth replacement rate, formation time, crown volume, total dentition volume, and enamel thickness for two coexisting but distantly related and morphologically disparate sauropod dinosaurs Camarasaurus and Diplodocus. Individual tooth formation time was determined by counting daily incremental lines in dentin. Tooth replacement rate is calculated as the difference between the number of days recorded in successive replacement teeth. Each tooth family in Camarasaurus has a maximum of three replacement teeth, whereas each Diplodocus tooth family has up to five. Tooth formation times are about 1.7 times longer in Camarasaurus than in Diplodocus (315 vs. 185 days. Average tooth replacement rate in Camarasaurus is about one tooth every 62 days versus about one tooth every 35 days in Diplodocus. Despite slower tooth replacement rates in Camarasaurus, the volumetric rate of Camarasaurus tooth replacement is 10 times faster than in Diplodocus because of its substantially greater tooth volumes. A novel method to estimate replacement rate was developed and applied to several other sauropodomorphs that we were not able to thin section. CONCLUSIONS/SIGNIFICANCE: Differences in tooth replacement rate among sauropodomorphs likely reflect disparate feeding strategies and/or food choices, which would have facilitated the coexistence of these gigantic herbivores in one ecosystem. Early neosauropods are characterized by high tooth replacement rates (despite their large tooth size, and derived titanosaurs and

  8. On a dinosaur axis from one of the oldest dinosaur-bearing sites worldwide

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    Rodrigo T. Müller

    2017-09-01

    Full Text Available The axial skeleton is proportionally underrepresented in the fossil record of early dinosaurs, when compared to other skeletal parts (e.g., pelvic girdle and hindlimb. For instance, the axis is poorly known in early dinosaurs, which precludes a better understanding of this important anatomical structure. Therefore, the present contribution fills an important gap with a description of the axis of a new early dinosaur (CAPPA/UFSM 0179. The specimen was collected at the Buriol outcrop, a Triassic fossiliferous locality from southern Brazil (Candelária Sequence, Santa Maria Supersequence biostratigraphically correlated to Carnian units, placing this specimen among the oldest dinosaurs worldwide. Notable features include the combination of a neural spine that bears an almost straight dorsal margin along its length and presence of an epipophysis. This axis arrangement is unique among Carnian dinosaurs, representing a new morphotype, though a similar morphology is observed in some early theropods. Indeed, a phylogenetic analysis nested the specimen within Theropoda. However, this outcome is probably biased by the large amount of missing data in CAPPA/UFSM 0179 and also due to the limited sampling of the axis in early dinosaurs, particularly among sauropodomorphs. As the specimen comes from the site that includes Buriolestes schultzi (an early sauropodomorph, it is quite plausible that CAPPA/UFSM 0179 might be referable to that taxon. If so, the specimen improves the anatomical knowledge of Buriolestes schultzi, given its axis is yet unknown. An alternative possibility to be considered is that the specimen would belong to a dinosaur not yet known in the Candelária Sequence, which would increase its dinosaur diversity for the outcrop, improving the Triassic dinosaurian record from Southern Brazil.

  9. Evolution of high tooth replacement rates in sauropod dinosaurs.

    Science.gov (United States)

    D'Emic, Michael D; Whitlock, John A; Smith, Kathlyn M; Fisher, Daniel C; Wilson, Jeffrey A

    2013-01-01

    Tooth replacement rate can be calculated in extinct animals by counting incremental lines of deposition in tooth dentin. Calculating this rate in several taxa allows for the study of the evolution of tooth replacement rate. Sauropod dinosaurs, the largest terrestrial animals that ever evolved, exhibited a diversity of tooth sizes and shapes, but little is known about their tooth replacement rates. We present tooth replacement rate, formation time, crown volume, total dentition volume, and enamel thickness for two coexisting but distantly related and morphologically disparate sauropod dinosaurs Camarasaurus and Diplodocus. Individual tooth formation time was determined by counting daily incremental lines in dentin. Tooth replacement rate is calculated as the difference between the number of days recorded in successive replacement teeth. Each tooth family in Camarasaurus has a maximum of three replacement teeth, whereas each Diplodocus tooth family has up to five. Tooth formation times are about 1.7 times longer in Camarasaurus than in Diplodocus (315 vs. 185 days). Average tooth replacement rate in Camarasaurus is about one tooth every 62 days versus about one tooth every 35 days in Diplodocus. Despite slower tooth replacement rates in Camarasaurus, the volumetric rate of Camarasaurus tooth replacement is 10 times faster than in Diplodocus because of its substantially greater tooth volumes. A novel method to estimate replacement rate was developed and applied to several other sauropodomorphs that we were not able to thin section. Differences in tooth replacement rate among sauropodomorphs likely reflect disparate feeding strategies and/or food choices, which would have facilitated the coexistence of these gigantic herbivores in one ecosystem. Early neosauropods are characterized by high tooth replacement rates (despite their large tooth size), and derived titanosaurs and diplodocoids independently evolved the highest known tooth replacement rates among archosaurs.

  10. Evolution and Function of Dinosaur Teeth at Ultramicrostructural Level Revealed Using Synchrotron Transmission X-ray Microscopy.

    Science.gov (United States)

    Wang, Chun-Chieh; Song, Yen-Fang; Song, Sheng-Rong; Ji, Qiang; Chiang, Cheng-Cheng; Meng, Qingjin; Li, Haibing; Hsiao, Kiko; Lu, Yi-Chia; Shew, Bor-Yuan; Huang, Timothy; Reisz, Robert R

    2015-10-29

    The relationship between tooth form and dietary preference is a crucial issue in vertebrate evolution. However, the mechanical properties of a tooth are influenced not only by its shape but also by its internal structure. Here, we use synchrotron transmission X-ray microscopy to examine the internal microstructures of multiple dinosaur teeth within a phylogenetic framework. We found that the internal microstructures of saurischian teeth are very different from advanced ornithischian teeth, reflecting differences in dental developmental strategies. The three-tissue composition (enamel-mantle dentin-bulk dentin) near the dentinoenamel junction (DEJ) in saurischian teeth represents the primitive condition of dinosaur teeth. Mantle dentin, greatly reduced or absent from DEJ in derived ornithischian teeth, is a key difference between Saurischia and Ornithischia. This may be related to the derived herbivorous feeding behavior of ornithischians, but interestingly, it is still retained in the herbivorous saurischian sauropods. The protective functions of mantle dentin with porous microstructures between enamel and bulk dentin inside typical saurischian teeth are also discussed using finite-element analysis method. Evolution of the dental modifications in ornithischian dinosaurs, with the absence of mantle dentin, may be related to changes in enamel characteristics with enamel spindles extending through the DEJ.

  11. CRETACEOUS CLIMATE SENSITIVITY STUDY USING DINOSAUR & PLANT PALEOBIOGEOGRAPHY

    Science.gov (United States)

    Goswami, A.; Main, D. J.; Noto, C. R.; Moore, T. L.; Scotese, C.

    2009-12-01

    The Early Cretaceous was characterized by cool poles and moderate global temperatures (~16° C). During the mid and late Cretaceous, long-term global warming (~20° - 22° C) was driven by increasing levels of CO2, rising sea level (lowering albedo) and the continuing breakup of Pangea. Paleoclimatic reconstructions for four time intervals during the Cretaceous: Middle Campanian (80 Ma), Cenomanian/Turonian (90 Ma), Early Albian (110 Ma) and Barremian-Hauterivian (130Ma) are presented here. These paleoclimate simulations were prepared using the Fast Ocean and Atmosphere Model (FOAM). The simulated results show the pattern of the pole-to-Equator temperature gradients, rainfall, surface run-off, the location of major rivers and deltas. In order to investigate the effect of potential dispersal routes on paleobiogeographic patterns, a time-slice series of maps from Early - Late Cretaceous were produced showing plots of dinosaur and plant fossil distributions. These Maps were created utilizing: 1) plant fossil localities from the GEON and Paleobiology (PBDB) databases; and 2) dinosaur fossil localities from an updated version of the Dinosauria (Weishampel, 2004) database. These results are compared to two different types of datasets, 1) Paleotemperature database for the Cretaceous and 2) locality data obtained from GEON, PBDB and Dinosauria database. Global latitudinal mean temperatures from both the model and the paelotemperature database were plotted on a series of latitudinal graphs along with the distributions of fossil plants and dinosaurs. It was found that most dinosaur localities through the Cretaceous tend to cluster within specific climate belts, or envelopes. Also, these Cretaceous maps show variance in biogeographic zonation of both plants and dinosaurs that is commensurate with reconstructed climate patterns and geography. These data are particularly useful for understanding the response of late Mesozoic ecosystems to geographic and climatic conditions that

  12. Cranial ontogenetic variation in early saurischians and the role of heterochrony in the diversification of predatory dinosaurs.

    Science.gov (United States)

    Foth, Christian; Hedrick, Brandon P; Ezcurra, Martin D

    2016-01-01

    Non-avian saurischian skulls underwent at least 165 million years of evolution and shapes varied from elongated skulls, such as in the theropod Coelophysis, to short and box-shaped skulls, such as in the sauropod Camarasaurus. A number of factors have long been considered to drive skull shape, including phylogeny, dietary preferences and functional constraints. However, heterochrony is increasingly being recognized as an important factor in dinosaur evolution. In order to quantitatively analyse the impact of heterochrony on saurischian skull shape, we analysed five ontogenetic trajectories using two-dimensional geometric morphometrics in a phylogenetic framework. This allowed for the comparative investigation of main ontogenetic shape changes and the evaluation of how heterochrony affected skull shape through both ontogenetic and phylogenetic trajectories. Using principal component analyses and multivariate regressions, it was possible to quantify different ontogenetic trajectories and evaluate them for evidence of heterochronic events allowing testing of previous hypotheses on cranial heterochrony in saurischians. We found that the skull shape of the hypothetical ancestor of Saurischia likely led to basal Sauropodomorpha through paedomorphosis, and to basal Theropoda mainly through peramorphosis. Paedomorphosis then led from Orionides to Avetheropoda, indicating that the paedomorphic trend found by previous authors in advanced coelurosaurs may extend back into the early evolution of Avetheropoda. Not only are changes in saurischian skull shape complex due to the large number of factors that affected it, but heterochrony itself is complex, with a number of possible reversals throughout non-avian saurischian evolution. In general, the sampling of complete ontogenetic trajectories including early juveniles is considerably lower than the sampling of single adult or subadult individuals, which is a major impediment to the study of heterochrony on non-avian dinosaurs

  13. Bone cells in birds show exceptional surface area, a characteristic tracing back to saurischian dinosaurs of the late Triassic.

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    Rensberger, John M; Martínez, Ricardo N

    2015-01-01

    Dinosaurs are unique among terrestrial tetrapods in their body sizes, which range from less than 3 gm in hummingbirds to 70,000 kg or more in sauropods. Studies of the microstructure of bone tissue have indicated that large dinosaurs, once believed to be slow growing, attained maturity at rates comparable to or greater than those of large mammals. A number of structural criteria in bone tissue have been used to assess differences in rates of osteogenesis in extinct taxa, including counts of lines of arrested growth and the density of vascular canals. Here, we examine the density of the cytoplasmic surface of bone-producing cells, a feature which may set an upper limit to the rate of osteogenesis. Osteocyte lacunae and canaliculi, the cavities in bone containing osteocytes and their extensions, were measured in thin-sections of primary (woven and parallel fibered) bone in a diversity of tetrapods. The results indicate that bone cell surfaces are more densely organized in the Saurischia (extant birds, extinct Mesozoic Theropoda and Sauropodomorpha) than in other tetrapods, a result of denser branching of the cell extensions. The highest postnatal growth rates among extant tetrapods occur in modern birds, the only surviving saurischians, and the finding of exceptional cytoplasmic surface area of the cells that produce bone in this group suggests a relationship with bone growth rate. In support of this relationship is finding the lowest cell surface density among the saurischians examined in Dinornis, a member of a group of ratites that evolved in New Zealand in isolation from mammalian predators and show other evidence of lowered maturation rates.

  14. A late-surviving basal theropod dinosaur from the latest Triassic of North America.

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    Sues, Hans-Dieter; Nesbitt, Sterling J; Berman, David S; Henrici, Amy C

    2011-11-22

    The oldest theropod dinosaurs are known from the Carnian of Argentina and Brazil. However, the evolutionary diversification of this group after its initial radiation but prior to the Triassic-Jurassic boundary is still poorly understood because of a sparse fossil record near that boundary. Here, we report on a new basal theropod, Daemonosaurus chauliodus gen. et sp. nov., from the latest Triassic 'siltstone member' of the Chinle Formation of the Coelophysis Quarry at Ghost Ranch, New Mexico. Based on a comprehensive phylogenetic analysis, Daemonosaurus is more closely related to coeval neotheropods (e.g. Coelophysis bauri) than to Herrerasauridae and Eoraptor. The skeletal structure of Daemonosaurus and the recently discovered Tawa bridge a morphological gap between Eoraptor and Herrerasauridae on one hand and neotheropods on the other, providing additional support for the theropod affinities of both Eoraptor and Herrerasauridae and demonstrating that lineages from the initial radiation of Dinosauria persisted until the end of the Triassic. Various features of the skull of Daemonosaurus, including the procumbent dentary and premaxillary teeth and greatly enlarged premaxillary and anterior maxillary teeth, clearly set this taxon apart from coeval neotheropods and demonstrate unexpected disparity in cranial shape among theropod dinosaurs just prior to the end of the Triassic.

  15. Head size, weaponry, and cervical adaptation: Testing craniocervical evolutionary hypotheses in Ceratopsia.

    Science.gov (United States)

    VanBuren, Collin S; Campione, Nicolás E; Evans, David C

    2015-07-01

    The anterior cervical vertebrae form the skeletal connection between the cranial and postcranial skeletons in higher tetrapods. As a result, the morphology of the atlas-axis complex is likely to be shaped by selection pressures acting on either the head or neck. The neoceratopsian (Reptilia:Dinosauria) syncervical represents one of the most highly modified atlas-axis regions in vertebrates, being formed by the complete coalescence of the three most anterior cervical vertebrae. In ceratopsids, the syncervical has been hypothesized to be an adaptation to support a massive skull, or to act as a buttress during intraspecific head-to-head combat. Here, we test these functional/adaptive hypotheses within a phylogenetic framework and critically examine the previously proposed methods for quantifying relative head size in the fossil record for the first time. Results indicate that neither the evolution of cranial weaponry nor large head size correlates with the origin of cervical fusion in ceratopsians, and we, therefore, reject both adaptive hypotheses for the origin of the syncervical. Anterior cervical fusion has evolved independently in a number of amniote clades, and further research on extant groups with this peculiar anatomy is needed to understand the evolutionary basis for cervical fusion in Neoceratopsia. © 2015 The Author(s). Evolution © 2015 The Society for the Study of Evolution.

  16. A palaeoequatorial ornithischian and new constraints on early dinosaur diversification.

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    Barrett, Paul M; Butler, Richard J; Mundil, Roland; Scheyer, Torsten M; Irmis, Randall B; Sánchez-Villagra, Marcelo R

    2014-09-22

    Current characterizations of early dinosaur evolution are incomplete: existing palaeobiological and phylogenetic scenarios are based on a fossil record dominated by saurischians and the implications of the early ornithischian record are often overlooked. Moreover, the timings of deep phylogenetic divergences within Dinosauria are poorly constrained owing to the absence of a rigorous chronostratigraphical framework for key Late Triassic-Early Jurassic localities. A new dinosaur from the earliest Jurassic of the Venezuelan Andes is the first basal ornithischian recovered from terrestrial deposits directly associated with a precise radioisotopic date and the first-named dinosaur from northern South America. It expands the early palaeogeographical range of Ornithischia to palaeoequatorial regions, an area sometimes thought to be devoid of early dinosaur taxa, and offers insights into early dinosaur growth rates, the evolution of sociality and the rapid tempo of the global dinosaur radiation following the end-Triassic mass extinction, helping to underscore the importance of the ornithischian record in broad-scale discussions of early dinosaur history. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

  17. The earliest bird-line archosaurs and the assembly of the dinosaur body plan.

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    Nesbitt, Sterling J; Butler, Richard J; Ezcurra, Martín D; Barrett, Paul M; Stocker, Michelle R; Angielczyk, Kenneth D; Smith, Roger M H; Sidor, Christian A; Niedźwiedzki, Grzegorz; Sennikov, Andrey G; Charig, Alan J

    2017-04-27

    The relationship between dinosaurs and other reptiles is well established, but the sequence of acquisition of dinosaurian features has been obscured by the scarcity of fossils with transitional morphologies. The closest extinct relatives of dinosaurs either have highly derived morphologies or are known from poorly preserved or incomplete material. Here we describe one of the stratigraphically lowest and phylogenetically earliest members of the avian stem lineage (Avemetatarsalia), Teleocrater rhadinus gen. et sp. nov., from the Middle Triassic epoch. The anatomy of T. rhadinus provides key information that unites several enigmatic taxa from across Pangaea into a previously unrecognized clade, Aphanosauria. This clade is the sister taxon of Ornithodira (pterosaurs and birds) and shortens the ghost lineage inferred at the base of Avemetatarsalia. We demonstrate that several anatomical features long thought to characterize Dinosauria and dinosauriforms evolved much earlier, soon after the bird-crocodylian split, and that the earliest avemetatarsalians retained the crocodylian-like ankle morphology and hindlimb proportions of stem archosaurs and early pseudosuchians. Early avemetatarsalians were substantially more species-rich, widely geographically distributed and morphologically diverse than previously recognized. Moreover, several early dinosauromorphs that were previously used as models to understand dinosaur origins may represent specialized forms rather than the ancestral avemetatarsalian morphology.

  18. Lower limits of ornithischian dinosaur body size inferred from a new Upper Jurassic heterodontosaurid from North America

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    Butler, Richard J.; Galton, Peter M.; Porro, Laura B.; Chiappe, Luis M.; Henderson, Donald M.; Erickson, Gregory M.

    2010-01-01

    The extremes of dinosaur body size have long fascinated scientists. The smallest (dinosaurs are carnivorous saurischian theropods, and similarly diminutive herbivorous or omnivorous ornithischians (the other major group of dinosaurs) are unknown. We report a new ornithischian dinosaur, Fruitadens haagarorum, from the Late Jurassic of western North America that rivals the smallest theropods in size. The largest specimens of Fruitadens represent young adults in their fifth year of development and are estimated at just 65–75 cm in total body length and 0.5–0.75 kg body mass. They are thus the smallest known ornithischians. Fruitadens is a late-surviving member of the basal dinosaur clade Heterodontosauridae, and is the first member of this clade to be described from North America. The craniodental anatomy and diminutive body size of Fruitadens suggest that this taxon was an ecological generalist with an omnivorous diet, thus providing new insights into morphological and palaeoecological diversity within Dinosauria. Late-surviving (Late Jurassic and Early Cretaceous) heterodontosaurids are smaller and less ecologically specialized than Early (Late Triassic and Early Jurassic) heterodontosaurids, and this ecological generalization may account in part for the remarkable 100-million-year-long longevity of the clade. PMID:19846460

  19. Global aspects of dinosaur distribution and evolution

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    Sues, H.

    1988-02-01

    Late Jurassic dinosaurian assemblages show close taxonomic correspondence over wide geographical ranges. Presently available if meager evidence suggests that this is also the case for Early Cretaceous communities. Cretaceous dinosaurian assemblages of Campanian and Maastrichtian age show considerable geographical differentiation but also some wide-ranging genera. Northern Hemisphere terrestrial ecosystems were dominated by hadrosaurs and ceratopsians, both herbivores with advanced capabilities for oral food-processing, whereas Southern Hemisphere biota were characterized by the abundance of titanosaurid sauropods, which relied on gut processing. Very close taxonomic similarities exist between the Campanian and early Maastrichtian dinosaurian assemblages of Mongolia and western North America, which, in part, is matched by similarities among other tetrapods such as mammals. Endemic dinosaurs in the Southern Hemisphere appear to reflect major changes in continental configuration. Some evidence exists for interchange of fuanal elements between North and South America. In absence of late Maastrichtian dinosaurian assemblages from most regions, scenarios concerning the terminal Cretaceous extinction of the Dinosauria should be regarded with caution because they are exclusively based on the conditions in western North America.

  20. Anomalously high variation in postnatal development is ancestral for dinosaurs but lost in birds

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    Griffin, Christopher T.; Nesbitt, Sterling J.

    2016-12-01

    Compared with all other living reptiles, birds grow extremely fast and possess unusually low levels of intraspecific variation during postnatal development. It is now clear that birds inherited their high rates of growth from their dinosaurian ancestors, but the origin of the avian condition of low variation during development is poorly constrained. The most well-understood growth trajectories of later Mesozoic theropods (e.g., Tyrannosaurus, Allosaurus) show similarly low variation to birds, contrasting with higher variation in extant crocodylians. Here, we show that deep within Dinosauria, among the earliest-diverging dinosaurs, anomalously high intraspecific variation is widespread but then is lost in more derived theropods. This style of development is ancestral for dinosaurs and their closest relatives, and, surprisingly, this level of variation is far higher than in living crocodylians. Among early dinosaurs, this variation is widespread across Pangaea in the Triassic and Early Jurassic, and among early-diverging theropods (ceratosaurs), this variation is maintained for 165 million years to the end of the Cretaceous. Because the Late Triassic environment across Pangaea was volatile and heterogeneous, this variation may have contributed to the rise of dinosaurian dominance through the end of the Triassic Period.

  1. Probabilistic divergence time estimation without branch lengths: dating the origins of dinosaurs, avian flight and crown birds.

    Science.gov (United States)

    Lloyd, G T; Bapst, D W; Friedman, M; Davis, K E

    2016-11-01

    Branch lengths-measured in character changes-are an essential requirement of clock-based divergence estimation, regardless of whether the fossil calibrations used represent nodes or tips. However, a separate set of divergence time approaches are typically used to date palaeontological trees, which may lack such branch lengths. Among these methods, sophisticated probabilistic approaches have recently emerged, in contrast with simpler algorithms relying on minimum node ages. Here, using a novel phylogenetic hypothesis for Mesozoic dinosaurs, we apply two such approaches to estimate divergence times for: (i) Dinosauria, (ii) Avialae (the earliest birds) and (iii) Neornithes (crown birds). We find: (i) the plausibility of a Permian origin for dinosaurs to be dependent on whether Nyasasaurus is the oldest dinosaur, (ii) a Middle to Late Jurassic origin of avian flight regardless of whether Archaeopteryx or Aurornis is considered the first bird and (iii) a Late Cretaceous origin for Neornithes that is broadly congruent with other node- and tip-dating estimates. Demonstrating the feasibility of probabilistic time-scaling further opens up divergence estimation to the rich histories of extinct biodiversity in the fossil record, even in the absence of detailed character data. © 2016 The Authors.

  2. Vertebral Adaptations to Large Body Size in Theropod Dinosaurs.

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    Wilson, John P; Woodruff, D Cary; Gardner, Jacob D; Flora, Holley M; Horner, John R; Organ, Chris L

    2016-01-01

    Rugose projections on the anterior and posterior aspects of vertebral neural spines appear throughout Amniota and result from the mineralization of the supraspinous and interspinous ligaments via metaplasia, the process of permanent tissue-type transformation. In mammals, this metaplasia is generally pathological or stress induced, but is a normal part of development in some clades of birds. Such structures, though phylogenetically sporadic, appear throughout the fossil record of non-avian theropod dinosaurs, yet their physiological and adaptive significance has remained unexamined. Here we show novel histologic and phylogenetic evidence that neural spine projections were a physiological response to biomechanical stress in large-bodied theropod species. Metaplastic projections also appear to vary between immature and mature individuals of the same species, with immature animals either lacking them or exhibiting smaller projections, supporting the hypothesis that these structures develop through ontogeny as a result of increasing bending stress subjected to the spinal column. Metaplastic mineralization of spinal ligaments would likely affect the flexibility of the spinal column, increasing passive support for body weight. A stiff spinal column would also provide biomechanical support for the primary hip flexors and, therefore, may have played a role in locomotor efficiency and mobility in large-bodied species. This new association of interspinal ligament metaplasia in Theropoda with large body size contributes additional insight to our understanding of the diverse biomechanical coping mechanisms developed throughout Dinosauria, and stresses the significance of phylogenetic methods when testing for biological trends, evolutionary or not.

  3. Eleven new species of Begonia (Begoniaceae from Sarawak, Borneo

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    Che-Wei Lin

    2017-08-01

    Full Text Available Diverse geological formations resulted in diverse terrains and varied microhabitats in Borneo where over 200 species of Begonia are currently known. The majority of Begonia species in Sarawak have a very narrow to moderately restricted distribution, and are often confined to a particular geology. An overwhelming number of new species were reported recently from Borneo. It was estimated that more than 600 species of Begonia occur in Borneo, which means that many more species are yet to be discovered and scientifically named. In continuation of our research on Sarawak Begonia, we discovered a number of unknown species of Begonia from southwestern Sarawak. Consultation of the literature, herbarium specimens and detailed morphological examination of plants in cultivation supports the recognition of eleven new species. Herein we name them as B. aiensis, B. dinosauria, B. hirsuticarpa, B. iridifolia, B. lawii, B. lichenora, B. magnicarpa, B. metallicolor, B. nix, B. superciliaris and B. wallacei, all of which belonging to sect. Petermannia. They are fully described and illustrated in this article.

  4. Mesozoic dinosaurs from Brazil and their biogeographic implications.

    Science.gov (United States)

    Bittencourt, Jonathas S; Langer, Max C

    2011-03-01

    The record of dinosaur body-fossils in the Brazilian Mesozoic is restricted to the Triassic of Rio Grande do Sul and Cretaceous of various parts of the country. This includes 21 named species, two of which were regarded as nomina dubia, and 19 consensually assigned to Dinosauria. Additional eight supraspecific taxa have been identified based on fragmentary specimens and numerous dinosaur footprints known in Brazil. In fact, most Brazilian specimens related to dinosaurs are composed of isolated teeth and vertebrae. Despite the increase of fieldwork during the last decade, there are still no dinosaur body-fossils of Jurassic age and the evidence of ornithischians in Brazil is very limited. Dinosaur faunas from this country are generally correlated with those from other parts of Gondwana throughout the Mesozoic. During the Late Triassic, there is a close correspondence to Argentina and other south-Pangaea areas. Mid-Cretaceous faunas of northeastern Brazil resemble those of coeval deposits of North Africa and Argentina. Southern hemisphere spinosaurids are restricted to Africa and Brazil, whereas abelisaurids are still unknown in the Early Cretaceous of the latter. Late Cretaceous dinosaur assemblages of south-central Brazil are endemic only to genus or, more conspicuously, to species level, sharing closely related taxa with Argentina, Madagascar, Indo-Pakistan and, to a lesser degree, continental Africa.

  5. Perennial Lakes as an Environmental Control on Theropod Movement in the Jurassic of the Hartford Basin

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    Patrick R. Getty

    2017-03-01

    Full Text Available Eubrontes giganteus is a common ichnospecies of large dinosaur track in the Early Jurassic rocks of the Hartford and Deerfield basins in Connecticut and Massachusetts, USA. It has been proposed that the trackmaker was gregarious based on parallel trackways at a site in Massachusetts known as Dinosaur Footprint Reservation (DFR. The gregariousness hypothesis is not without its problems, however, since parallelism can be caused by barriers that direct animal travel. We tested the gregariousness hypothesis by examining the orientations of trackways at five sites representing permanent and ephemeral lacustrine environments. Parallelism is only prominent in permanent lacustrine rocks at DFR, where trackways show a bimodal orientation distribution that approximates the paleoshoreline. By contrast, parallel trackways are uncommon in ephemeral lacustrine facies, even at sites with large numbers of trackways, and those that do occur exhibit differences in morphology, suggesting that they were made at different times. Overall, the evidence presented herein suggests that parallelism seen in Hartford Basin Eubrontes giganteus is better explained as a response to the lake acting as a physical barrier rather than to gregariousness. Consequently, these parallel trackways should not be used as evidence to support the hypothesis that the trackmaker was a basal sauropodomorph unless other evidence can substantiate the gregariousness hypothesis.

  6. How many dinosaur species were there? Fossil bias and true richness estimated using a Poisson sampling model.

    Science.gov (United States)

    Starrfelt, Jostein; Liow, Lee Hsiang

    2016-04-05

    The fossil record is a rich source of information about biological diversity in the past. However, the fossil record is not only incomplete but has also inherent biases due to geological, physical, chemical and biological factors. Our knowledge of past life is also biased because of differences in academic and amateur interests and sampling efforts. As a result, not all individuals or species that lived in the past are equally likely to be discovered at any point in time or space. To reconstruct temporal dynamics of diversity using the fossil record, biased sampling must be explicitly taken into account. Here, we introduce an approach that uses the variation in the number of times each species is observed in the fossil record to estimate both sampling bias and true richness. We term our technique TRiPS (True Richness estimated using a Poisson Sampling model) and explore its robustness to violation of its assumptions via simulations. We then venture to estimate sampling bias and absolute species richness of dinosaurs in the geological stages of the Mesozoic. Using TRiPS, we estimate that 1936 (1543-2468) species of dinosaurs roamed the Earth during the Mesozoic. We also present improved estimates of species richness trajectories of the three major dinosaur clades: the sauropodomorphs, ornithischians and theropods, casting doubt on the Jurassic-Cretaceous extinction event and demonstrating that all dinosaur groups are subject to considerable sampling bias throughout the Mesozoic. © 2016 The Authors.

  7. The anatomy of the bifurcated neural spine and its occurrence within Tetrapoda.

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    Woodruff, D Cary

    2014-09-01

    Vertebral neural spine bifurcation has been historically treated as largely restrictive to sauropodomorph dinosaurs; wherein it is inferred to be an adaptation in response to the increasing weight from the horizontally extended cervical column. Because no extant terrestrial vertebrates have massive, horizontally extended necks, extant forms with large cranial masses were examined for the presence of neural spine bifurcation. Here, I report for the first time on the soft tissue surrounding neural spine bifurcation in a terrestrial quadruped through the dissection of three Ankole-Watusi cattle. With horns weighing up to a combined 90 kg, the Ankole-Watusi is unlike any other breed of cattle in terms of cranial weight and presence of neural spine bifurcation. Using the Ankole-Watusi as a model, it appears that neural spine bifurcation plays a critical role in supporting a large mobile weight adjacent to the girdles. In addition to neural spine bifurcation being recognized within nonavian dinosaurs, this vertebral feature is also documented within many members of temnospondyls, captorhinids, seymouriamorphs, diadectomorphs, Aves, marsupials, artiodactyls, perissodactyls, and Primates, amongst others. This phylogenetic distribution indicates that spine bifurcation is more common than previously thought, and that this vertebral adaptation has contributed throughout the evolutionary history of tetrapods. Neural spine bifurcation should now be recognized as an anatomical component adapted by some vertebrates to deal with massive, horizontal, mobile weights adjacent the girdles. © 2014 Wiley Periodicals, Inc.

  8. Forearm posture and mobility in quadrupedal dinosaurs.

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    VanBuren, Collin S; Bonnan, Matthew

    2013-01-01

    Quadrupedality evolved four independent times in dinosaurs; however, the constraints associated with these transitions in limb anatomy and function remain poorly understood, in particular the evolution of forearm posture and rotational ability (i.e., active pronation and supination). Results of previous qualitative studies are inconsistent, likely due to an inability to quantitatively assess the likelihood of their conclusions. We attempt to quantify antebrachial posture and mobility using the radius bone because its morphology is distinct between extant sprawled taxa with a limited active pronation ability and parasagittal taxa that have an enhanced ability to actively pronate the manus. We used a sliding semi-landmark, outline-based geometric morphometric approach of the proximal radial head and a measurement of the angle of curvature of the radius in a sample of 189 mammals, 49 dinosaurs, 35 squamates, 16 birds, and 5 crocodilians. Our results of radial head morphology showed that quadrupedal ceratopsians, bipedal non-hadrosaurid ornithopods, and theropods had limited pronation/supination ability, and sauropodomorphs have unique radial head morphology that likely allowed limited rotational ability. However, the curvature of the radius showed that no dinosaurian clade had the ability to cross the radius about the ulna, suggesting parallel antebrachial elements for all quadrupedal dinosaurs. We conclude that the bipedal origins of all quadrupedal dinosaur clades could have allowed for greater disparity in forelimb posture than previously appreciated, and future studies on dinosaur posture should not limit their classifications to the overly simplistic extant dichotomy.

  9. Morphological Diversity and Evolution of the Jugal in Dinosaurs.

    Science.gov (United States)

    Sullivan, Corwin; Xu, Xing

    2017-01-01

    In dinosaurs, as in other reptiles, the homologue of the mammalian zygomatic bone is the jugal. The dinosaurian jugal was primitively triradiate, with posterior, dorsal and anterior processes that respectively contacted the quadratojugal, the postorbital, and the maxilla and lacrimal. However, the jugal evolved along different lines in the three major dinosaurian clades. In theropods this cranial element remained relatively conservative in morphology, apart from being reduced to a rod-like structure in most birds and a few non-avians. In sauropodomorphs the jugal eventually became small, plate-like and nearly restricted to the area below the orbit, even being excluded from the ventral margin of the skull in many derived taxa. Among ornithischians the jugal was highly variable, but in many cases became large and/or adorned with ornamental features such as horns, flanges, and rugosities. The jugal does not appear to have been a site of muscle attachment in most non-avian dinosaurs, but represented an important structural element in the akinetic dinosaurian skull. The conspicuous jugal ornaments seen in many ornithischian dinosaurs, like the less striking ones documented in some saurischians, may have played an important role in the social behavior of the species that possessed them. In many cases they have a weapon-like aspect suggesting use in aggressive displays, if not actual combat, adding to the evidence that agonistic behavior was likely widespread among ornithischians in particular. Anat Rec, 300:30-48, 2017. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  10. Forearm posture and mobility in quadrupedal dinosaurs.

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    Collin S VanBuren

    Full Text Available Quadrupedality evolved four independent times in dinosaurs; however, the constraints associated with these transitions in limb anatomy and function remain poorly understood, in particular the evolution of forearm posture and rotational ability (i.e., active pronation and supination. Results of previous qualitative studies are inconsistent, likely due to an inability to quantitatively assess the likelihood of their conclusions. We attempt to quantify antebrachial posture and mobility using the radius bone because its morphology is distinct between extant sprawled taxa with a limited active pronation ability and parasagittal taxa that have an enhanced ability to actively pronate the manus. We used a sliding semi-landmark, outline-based geometric morphometric approach of the proximal radial head and a measurement of the angle of curvature of the radius in a sample of 189 mammals, 49 dinosaurs, 35 squamates, 16 birds, and 5 crocodilians. Our results of radial head morphology showed that quadrupedal ceratopsians, bipedal non-hadrosaurid ornithopods, and theropods had limited pronation/supination ability, and sauropodomorphs have unique radial head morphology that likely allowed limited rotational ability. However, the curvature of the radius showed that no dinosaurian clade had the ability to cross the radius about the ulna, suggesting parallel antebrachial elements for all quadrupedal dinosaurs. We conclude that the bipedal origins of all quadrupedal dinosaur clades could have allowed for greater disparity in forelimb posture than previously appreciated, and future studies on dinosaur posture should not limit their classifications to the overly simplistic extant dichotomy.

  11. A simulated bird gastric mill and its implications for fossil gastrolith authenticity

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    O. Wings

    2009-02-01

    Full Text Available A rock tumbler, stones, water, plant material, hydrochloric acid, and pepsin were used to simulate a bird gizzard in order to study abrasion rate and influence of stomach juices and foodstuff on gastrolith surface development. The experiment lasted for six months. Each week, the "stomach" was supplied with fresh grass and stomach juices. After the end of the experiment, the set of stones had a combined weight loss of 22.4%, with softer rock types showing higher abrasion rates. The combination of stomach juices and silica phytoliths within the grass had no visible effect on stone surface development: polish or pitting did not occur. A second experiment combined only pebbles with water in the tumbler. Results indicate that rock abrasion is mainly caused by contacts between moving stones. A comparison with authentic ostrich gastroliths showed that abrasion in the artificial stomach must have been lower than in a real gizzard, but still too high to maintain or develop surface polish. If high polish occasionally seen on sauropodomorph dinosaur gastroliths was indeed caused in a stomach environment, it implies digestive processes different from those of extant birds and the "artificial gizzard". Geologic origins of polish, such as transport in hyperconcentrated flows, wind blasting, or tectonic movements must be considered for polished fossil gastroliths and isolated clasts in fine-grained sediments (exoliths. doi:10.1002/mmng.200800013

  12. Limb bone allometry during postnatal ontogeny in non-avian dinosaurs

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    Kilbourne, Brandon M; Makovicky, Peter J

    2010-01-01

    Although the interspecific scaling of tetrapods is well understood, remarkably little work has been done on the ontogenetic scaling within tetrapod species, whether fossil or recent. Here the ontogenetic allometry of the femur, humerus, and tibia was determined for 23 species of non-avian dinosaur by regressing log-transformed length against log-transformed circumference for each bone using reduced major axis bivariate regression. The femora of large theropod species became more robust during ontogeny, whereas growth in the femora of sauropodomorphs and most ornithischians was not significantly different from isometry. Hadrosaur hindlimb elements became significantly more gracile during ontogeny. Scaling constants were higher in all theropods than in any non-theropod taxa. Such clear taxonomically correlated divisions were not evident in the ontogenetic allometry of the tibia and hindlimb bones did not scale uniformly within larger taxonomic groups. For taxa in which the ontogenetic allometry of the humerus was studied, only Riojasaurus incertus exhibited a significant departure from isometry. Using independent contrasts, the regression of femoral allometry against the log of adult body mass was found to have a significant negative correlation but such a relationship could not be established for other limb elements or growth parameters, mainly due to the small sample size. The intraspecific scaling patterns observed in dinosaurs and other amniotes do not support earlier hypotheses that intraspecific scaling differs between endothermic and ectothermic taxa. PMID:20557400

  13. A new horned dinosaur reveals convergent evolution in cranial ornamentation in Ceratopsidae.

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    Brown, Caleb M; Henderson, Donald M

    2015-06-15

    Ceratopsid (horned) dinosaurs are an iconic group of large-bodied, quadrupedal, herbivorous dinosaurs that evolved in the Late Cretaceous and were largely restricted to western North America [1-5]. Ceratopsids are easily recognized by their cranial ornamentation in the form of nasal and postorbital horns and frill (capped by epiossifications); these structures show high morphological disparity and also represent the largest cranial display structures known to have evolved [2, 4]. Despite their restricted occurrence in time and space, this group has one of the best fossil records within Dinosauria, showing a rapid diversification in horn and frill morphology [1]. Here a new genus and species of chasmosaurine ceratopsid is described based on a nearly complete and three-dimensionally preserved cranium recovered from the uppermost St. Mary River Formation (Maastrichtian) of southwestern Alberta. Regaliceratops peterhewsi gen. et sp. nov. exhibits many unique characters of the frill and is characterized by a large nasal horncore, small postorbital horncores, and massive parietal epiossifications. Cranial morphology, particularly the epiossifications, suggests close affinity with the late Campanian/early Maastrichian taxon Anchiceratops, as well as with the late Maastrichtian taxon Triceratops. A median epiparietal necessitates a reassessment of epiossification homology and results in a more resolved phylogeny. Most surprisingly, Regaliceratops exhibits a suite of cranial ornamentations that are superficially similar to Campanian centrosaurines, indicating both exploration of novel display morphospace in Chasmosaurinae, especially Maastrichtian forms, and convergent evolution in horn morphology with the recently extinct Centrosaurinae. This marks the first time that evolutionary convergence in horn-like display structures has been demonstrated between dinosaur clades, similar to those seen in fossil and extant mammals [6]. Copyright © 2015 Elsevier Ltd. All rights

  14. Reidentification of avian embryonic remains from the cretaceous of mongolia.

    Science.gov (United States)

    Varricchio, David J; Balanoff, Amy M; Norell, Mark A

    2015-01-01

    Embryonic remains within a small (4.75 by 2.23 cm) egg from the Late Cretaceous, Mongolia are here re-described. High-resolution X-ray computed tomography (HRCT) was used to digitally prepare and describe the enclosed embryonic bones. The egg, IGM (Mongolian Institute for Geology, Ulaanbaatar) 100/2010, with a three-part shell microstructure, was originally assigned to Neoceratopsia implying extensive homoplasy among eggshell characters across Dinosauria. Re-examination finds the forelimb significantly longer than the hindlimbs, proportions suggesting an avian identification. Additional, postcranial apomorphies (strut-like coracoid, cranially located humeral condyles, olecranon fossa, slender radius relative to the ulna, trochanteric crest on the femur, and ulna longer than the humerus) identify the embryo as avian. Presence of a dorsal coracoid fossa and a craniocaudally compressed distal humerus with a strongly angled distal margin support a diagnosis of IGM 100/2010 as an enantiornithine. Re-identification eliminates the implied homoplasy of this tri-laminate eggshell structure, and instead associates enantiornithine birds with eggshell microstructure composed of a mammillary, squamatic, and external zones. Posture of the embryo follows that of other theropods with fore- and hindlimbs folded parallel to the vertebral column and the elbow pointing caudally just dorsal to the knees. The size of the egg and embryo of IGM 100/2010 is similar to the two other Mongolian enantiornithine eggs. Well-ossified skeletons, as in this specimen, characterize all known enantiornithine embryos suggesting precocial hatchlings, comparing closely to late stage embryos of modern precocial birds that are both flight- and run-capable upon hatching. Extensive ossification in enantiornithine embryos may contribute to their relatively abundant representation in the fossil record. Neoceratopsian eggs remain unrecognized in the fossil record.

  15. Reidentification of avian embryonic remains from the cretaceous of mongolia.

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    David J Varricchio

    Full Text Available Embryonic remains within a small (4.75 by 2.23 cm egg from the Late Cretaceous, Mongolia are here re-described. High-resolution X-ray computed tomography (HRCT was used to digitally prepare and describe the enclosed embryonic bones. The egg, IGM (Mongolian Institute for Geology, Ulaanbaatar 100/2010, with a three-part shell microstructure, was originally assigned to Neoceratopsia implying extensive homoplasy among eggshell characters across Dinosauria. Re-examination finds the forelimb significantly longer than the hindlimbs, proportions suggesting an avian identification. Additional, postcranial apomorphies (strut-like coracoid, cranially located humeral condyles, olecranon fossa, slender radius relative to the ulna, trochanteric crest on the femur, and ulna longer than the humerus identify the embryo as avian. Presence of a dorsal coracoid fossa and a craniocaudally compressed distal humerus with a strongly angled distal margin support a diagnosis of IGM 100/2010 as an enantiornithine. Re-identification eliminates the implied homoplasy of this tri-laminate eggshell structure, and instead associates enantiornithine birds with eggshell microstructure composed of a mammillary, squamatic, and external zones. Posture of the embryo follows that of other theropods with fore- and hindlimbs folded parallel to the vertebral column and the elbow pointing caudally just dorsal to the knees. The size of the egg and embryo of IGM 100/2010 is similar to the two other Mongolian enantiornithine eggs. Well-ossified skeletons, as in this specimen, characterize all known enantiornithine embryos suggesting precocial hatchlings, comparing closely to late stage embryos of modern precocial birds that are both flight- and run-capable upon hatching. Extensive ossification in enantiornithine embryos may contribute to their relatively abundant representation in the fossil record. Neoceratopsian eggs remain unrecognized in the fossil record.

  16. Cranial ontogenetic variation in early saurischians and the role of heterochrony in the diversification of predatory dinosaurs

    Directory of Open Access Journals (Sweden)

    Christian Foth

    2016-01-01

    Full Text Available Non-avian saurischian skulls underwent at least 165 million years of evolution and shapes varied from elongated skulls, such as in the theropod Coelophysis, to short and box-shaped skulls, such as in the sauropod Camarasaurus. A number of factors have long been considered to drive skull shape, including phylogeny, dietary preferences and functional constraints. However, heterochrony is increasingly being recognized as an important factor in dinosaur evolution. In order to quantitatively analyse the impact of heterochrony on saurischian skull shape, we analysed five ontogenetic trajectories using two-dimensional geometric morphometrics in a phylogenetic framework. This allowed for the comparative investigation of main ontogenetic shape changes and the evaluation of how heterochrony affected skull shape through both ontogenetic and phylogenetic trajectories. Using principal component analyses and multivariate regressions, it was possible to quantify different ontogenetic trajectories and evaluate them for evidence of heterochronic events allowing testing of previous hypotheses on cranial heterochrony in saurischians. We found that the skull shape of the hypothetical ancestor of Saurischia likely led to basal Sauropodomorpha through paedomorphosis, and to basal Theropoda mainly through peramorphosis. Paedomorphosis then led from Orionides to Avetheropoda, indicating that the paedomorphic trend found by previous authors in advanced coelurosaurs may extend back into the early evolution of Avetheropoda. Not only are changes in saurischian skull shape complex due to the large number of factors that affected it, but heterochrony itself is complex, with a number of possible reversals throughout non-avian saurischian evolution. In general, the sampling of complete ontogenetic trajectories including early juveniles is considerably lower than the sampling of single adult or subadult individuals, which is a major impediment to the study of heterochrony on

  17. First complete sauropod dinosaur skull from the Cretaceous of the Americas and the evolution of sauropod dentition

    Science.gov (United States)

    Chure, Daniel; Britt, Brooks B.; Whitlock, John A.; Wilson, Jeffrey A.

    2010-04-01

    Sauropod dinosaur bones are common in Mesozoic terrestrial sediments, but sauropod skulls are exceedingly rare—cranial materials are known for less than one third of sauropod genera and even fewer are known from complete skulls. Here we describe the first complete sauropod skull from the Cretaceous of the Americas, Abydosaurus mcintoshi, n. gen., n. sp., known from 104.46 ± 0.95 Ma (megannum) sediments from Dinosaur National Monument, USA. Abydosaurus shares close ancestry with Brachiosaurus, which appeared in the fossil record ca. 45 million years earlier and had substantially broader teeth. A survey of tooth shape in sauropodomorphs demonstrates that sauropods evolved broad crowns during the Early Jurassic but did not evolve narrow crowns until the Late Jurassic, when they occupied their greatest range of crown breadths. During the Cretaceous, brachiosaurids and other lineages independently underwent a marked diminution in tooth breadth, and before the latest Cretaceous broad-crowned sauropods were extinct on all continental landmasses. Differential survival and diversification of narrow-crowned sauropods in the Late Cretaceous appears to be a directed trend that was not correlated with changes in plant diversity or abundance, but may signal a shift towards elevated tooth replacement rates and high-wear dentition. Sauropods lacked many of the complex herbivorous adaptations present within contemporaneous ornithischian herbivores, such as beaks, cheeks, kinesis, and heterodonty. The spartan design of sauropod skulls may be related to their remarkably small size—sauropod skulls account for only 1/200th of total body volume compared to 1/30th body volume in ornithopod dinosaurs.

  18. Vascular Patterns in Iguanas and Other Squamates: Blood Vessels and Sites of Thermal Exchange.

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    William Ruger Porter

    Full Text Available Squamates use the circulatory system to regulate body and head temperatures during both heating and cooling. The flexibility of this system, which possibly exceeds that of endotherms, offers a number of physiological mechanisms to gain or retain heat (e.g., increase peripheral blood flow and heart rate, cooling the head to prolong basking time for the body as well as to shed heat (modulate peripheral blood flow, expose sites of thermal exchange. Squamates also have the ability to establish and maintain the same head-to-body temperature differential that birds, crocodilians, and mammals demonstrate, but without a discrete rete or other vascular physiological device. Squamates offer important anatomical and phylogenetic evidence for the inference of the blood vessels of dinosaurs and other extinct archosaurs in that they shed light on the basal diapsid condition. Given this basal positioning, squamates likewise inform and constrain the range of physiological thermoregulatory mechanisms that may have been found in Dinosauria. Unfortunately, the literature on squamate vascular anatomy is limited. Cephalic vascular anatomy of green iguanas (Iguana iguana was investigated using a differential-contrast, dual-vascular injection (DCDVI technique and high-resolution X-ray microcomputed tomography (μCT. Blood vessels were digitally segmented to create a surface representation of vascular pathways. Known sites of thermal exchange, consisting of the oral, nasal, and orbital regions, were given special attention due to their role in brain and cephalic thermoregulation. Blood vessels to and from sites of thermal exchange were investigated to detect conserved vascular patterns and to assess their ability to deliver cooled blood to the dural venous sinuses. Arteries within sites of thermal exchange were found to deliver blood directly and through collateral pathways. The venous drainage was found to have multiple pathways that could influence neurosensory

  19. Biology of the sauropod dinosaurs: the evolution of gigantism.

    Science.gov (United States)

    Sander, P Martin; Christian, Andreas; Clauss, Marcus; Fechner, Regina; Gee, Carole T; Griebeler, Eva-Maria; Gunga, Hanns-Christian; Hummel, Jürgen; Mallison, Heinrich; Perry, Steven F; Preuschoft, Holger; Rauhut, Oliver W M; Remes, Kristian; Tütken, Thomas; Wings, Oliver; Witzel, Ulrich

    2011-02-01

    extensive pneumatization of the axial skeleton resulted from the evolution of an avian-style respiratory system, presumably at the base of Saurischia. An avian-style respiratory system would also have lowered the cost of breathing, reduced specific gravity, and may have been important in removing excess body heat. Another crucial innovation inherited from basal dinosaurs was a high BMR. This is required for fueling the high growth rate necessary for a multi-tonne animal to survive to reproductive maturity. The retention of the plesiomorphic oviparous mode of reproduction appears to have been critical as well, allowing much faster population recovery than in megaherbivore mammals. Sauropods produced numerous but small offspring each season while land mammals show a negative correlation of reproductive output to body size. This permitted lower population densities in sauropods than in megaherbivore mammals but larger individuals. Our work on sauropod dinosaurs thus informs us about evolutionary limits to body size in other groups of herbivorous terrestrial tetrapods. Ectothermic reptiles are strongly limited by their low BMR, remaining small. Mammals are limited by their extensive mastication and their vivipary, while ornithsichian dinosaurs were only limited by their extensive mastication, having greater average body sizes than mammals. © 2010 The Authors. Biological Reviews © 2010 Cambridge Philosophical Society.

  20. A New Titanosaurian Braincase from the Cretaceous “Lo Hueco” Locality in Spain Sheds Light on Neuroanatomical Evolution within Titanosauria

    Science.gov (United States)

    Knoll, Fabien; Witmer, Lawrence M.; Ridgely, Ryan C.; Ortega, Francisco; Sanz, Jose Luis

    2015-01-01

    Despite continuous improvements, our knowledge of the neurocranial anatomy of sauropod dinosaurs as a whole is still poor, which is especially true for titanosaurians even though their postcranial remains are common in many Upper Cretaceous sites worldwide. Here we describe a braincase from the uppermost Cretaceous locality of ‘‘Lo Hueco” in Spain that is one of the most complete titanosaurian braincases found so far in Europe. Although the titanosaurian Ampelosaurus sp. is known from the same locality, this specimen is clearly a distinct taxon and presents a number of occipital characters found in Antarctosaurus and Jainosaurus, which are approximately coeval taxa from southern Gondwana. The specimen was subjected to X-ray computed tomographic (CT) scanning, allowing the generation of 3D renderings of the endocranial cavity enclosing the brain, cranial nerves, and blood vessels, as well as the labyrinth of the inner ear. These findings add considerable knowledge to the field of sauropod paleoneuroanatomy in general and titanosaurian endocast diversity in particular. Compared with that of many sauropodomorphs, the endocast appears only slightly flexed in lateral view and bears similarities (e.g., reduction of the rostral dural expansion) with Gondwanan titanosaurians such as Jainosaurus, Bonatitan, and Antarctosaurus. The vestibular system of the inner ear is somewhat contracted (i.e., the radius of the semicircular canals is small), but less so than expected in derived titanosaurians. However, as far as the new specimen and Jainosaurus can be contrasted, and with the necessary caution due to the small sample of comparative data currently available, the two taxa appear more similar to one another in endocast morphology than to other titanosaurians. Recent phylogenetic analyses of titanosaurians have not included virtually any of the taxa under consideration here, and thus the phylogenetic position of the new Spanish titanosaurian—even its generic, let alone

  1. Complete forelimb myology of the basal theropod dinosaur Tawa hallae based on a novel robust muscle reconstruction method.

    Science.gov (United States)

    Burch, Sara H

    2014-09-01

    The forelimbs of nonavian theropod dinosaurs have been the subject of considerable study and speculation due to their varied morphology and role in the evolution of flight. Although many studies on the functional morphology of a limb require an understanding of its musculature, comparatively little is known about the forelimb myology of theropods and other bipedal dinosaurs. Previous phylogenetically based myological reconstructions have been limited to the shoulder, restricting their utility in analyses of whole-limb function. The antebrachial and manual musculature in particular have remained largely unstudied due to uncertain muscular homologies in archosaurs. Through analysis of the musculature of extant taxa in a robust statistical framework, this study presents new hypotheses of homology for the distal limb musculature of archosaurs and provides the first complete reconstruction of dinosaurian forelimb musculature, including the antebrachial and intrinsic manual muscles. Data on the forelimb myology of a broad sample of extant birds, crocodylians, lizards, and turtles were analyzed using maximum likelihood ancestral state reconstruction and examined together with the osteology of the early theropod Tawa hallae from the Late Triassic of New Mexico to formulate a complete plesiomorphic myology for the theropod forelimb. Comparisons with previous reconstructions show that the shoulder musculature of basal theropods is more similar to that of basal ornithischians and sauropodomorphs than to that of dromaeosaurids. Greater development of the supracoracoideus and deltoideus musculature in theropods over other bipedal dinosaurs correlates with stronger movements of the forelimb at the shoulder and an emphasis on apprehension of relatively large prey. This emphasis is further supported by the morphology of the antebrachium and the intrinsic manual musculature, which exhibit a high degree of excursion and a robust morphology well-suited for powerful digital flexion

  2. Air-filled postcranial bones in theropod dinosaurs: physiological implications and the 'reptile'-bird transition.

    Science.gov (United States)

    Benson, Roger B J; Butler, Richard J; Carrano, Matthew T; O'Connor, Patrick M

    2012-02-01

    Pneumatic (air-filled) postcranial bones are unique to birds among extant tetrapods. Unambiguous skeletal correlates of postcranial pneumaticity first appeared in the Late Triassic (approximately 210 million years ago), when they evolved independently in several groups of bird-line archosaurs (ornithodirans). These include the theropod dinosaurs (of which birds are extant representatives), the pterosaurs, and sauropodomorph dinosaurs. Postulated functions of skeletal pneumatisation include weight reduction in large-bodied or flying taxa, and density reduction resulting in energetic savings during foraging and locomotion. However, the influence of these hypotheses on the early evolution of pneumaticity has not been studied in detail previously. We review recent work on the significance of pneumaticity for understanding the biology of extinct ornithodirans, and present detailed new data on the proportion of the skeleton that was pneumatised in 131 non-avian theropods and Archaeopteryx. This includes all taxa known from significant postcranial remains. Pneumaticity of the cervical and anterior dorsal vertebrae occurred early in theropod evolution. This 'common pattern' was conserved on the line leading to birds, and is likely present in Archaeopteryx. Increases in skeletal pneumaticity occurred independently in as many as 12 lineages, highlighting a remarkably high number of parallel acquisitions of a bird-like feature among non-avian theropods. Using a quantitative comparative framework, we show that evolutionary increases in skeletal pneumaticity are significantly concentrated in lineages with large body size, suggesting that mass reduction in response to gravitational constraints at large body sizes influenced the early evolution of pneumaticity. However, the body size threshold for extensive pneumatisation is lower in theropod lineages more closely related to birds (maniraptorans). Thus, relaxation of the relationship between body size and pneumatisation preceded

  3. The Evolution of Diapsid Reproductive Strategy with Inferences about Extinct Taxa.

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    Jason R Moore

    Full Text Available Diapsids show an extremely wide range of reproductive strategies. Offspring may receive no parental care, care from only one sex, care from both parents, or care under more complex regimes. Young may vary from independent, super-precocial hatchlings to altricial neonates needing much care before leaving the nest. Parents can invest heavily in a few young, or less so in a larger number. Here we examine the evolution of these traits across a composite phylogeny spanning the extant diapsids and including the limited number of extinct taxa for which reproductive strategies can be well constrained. Generalized estimating equation(GEE-based phylogenetic comparative methods demonstrate the influences of body mass, parental care strategy and hatchling maturity on clutch volume across the diapsids. The influence of polygamous reproduction is not important despite a large sample size. Applying the results of these models to the dinosaurs supports the hypothesis of paternal care (male only in derived non-avian theropods, previously suggested based on simpler analyses. These data also suggest that sauropodomorphs did not care for their young. The evolution of parental-care occurs in an almost linear series of transitions. Paternal care rarely gives rise to other care strategies. Where hatchling condition changes, diapsids show an almost unidirectional tendency of evolution towards increased altriciality. Transitions to social monogamy from the ancestral state in diapsids, where both sexes are polygamous, are common. In contrast, once evolved, polygyny and polyandry are very evolutionarily stable. Polygyny and maternal care correlate, as do polyandry and paternal care. Ancestral-character estimation (ACE of these care strategies with the character transition likelihoods estimated from the original data gives good confidence at most important nodes. These analyses suggest that the basalmost diapsids had no parental care. Crocodilians independently evolved

  4. A New Titanosaurian Braincase from the Cretaceous "Lo Hueco" Locality in Spain Sheds Light on Neuroanatomical Evolution within Titanosauria.

    Science.gov (United States)

    Knoll, Fabien; Witmer, Lawrence M; Ridgely, Ryan C; Ortega, Francisco; Sanz, Jose Luis

    2015-01-01

    Despite continuous improvements, our knowledge of the neurocranial anatomy of sauropod dinosaurs as a whole is still poor, which is especially true for titanosaurians even though their postcranial remains are common in many Upper Cretaceous sites worldwide. Here we describe a braincase from the uppermost Cretaceous locality of ''Lo Hueco" in Spain that is one of the most complete titanosaurian braincases found so far in Europe. Although the titanosaurian Ampelosaurus sp. is known from the same locality, this specimen is clearly a distinct taxon and presents a number of occipital characters found in Antarctosaurus and Jainosaurus, which are approximately coeval taxa from southern Gondwana. The specimen was subjected to X-ray computed tomographic (CT) scanning, allowing the generation of 3D renderings of the endocranial cavity enclosing the brain, cranial nerves, and blood vessels, as well as the labyrinth of the inner ear. These findings add considerable knowledge to the field of sauropod paleoneuroanatomy in general and titanosaurian endocast diversity in particular. Compared with that of many sauropodomorphs, the endocast appears only slightly flexed in lateral view and bears similarities (e.g., reduction of the rostral dural expansion) with Gondwanan titanosaurians such as Jainosaurus, Bonatitan, and Antarctosaurus. The vestibular system of the inner ear is somewhat contracted (i.e., the radius of the semicircular canals is small), but less so than expected in derived titanosaurians. However, as far as the new specimen and Jainosaurus can be contrasted, and with the necessary caution due to the small sample of comparative data currently available, the two taxa appear more similar to one another in endocast morphology than to other titanosaurians. Recent phylogenetic analyses of titanosaurians have not included virtually any of the taxa under consideration here, and thus the phylogenetic position of the new Spanish titanosaurian--even its generic, let alone

  5. Testing co-evolutionary hypotheses over geological timescales: interactions between Mesozoic non-avian dinosaurs and cycads.

    Science.gov (United States)

    Butler, Richard J; Barrett, Paul M; Kenrick, Paul; Penn, Malcolm G

    2009-02-01

    The significance of co-evolution over ecological timescales is well established, yet it remains unclear to what extent co-evolutionary processes contribute to driving large-scale evolutionary and ecological changes over geological timescales. Some of the most intriguing and pervasive long-term co-evolutionary hypotheses relate to proposed interactions between herbivorous non-avian dinosaurs and Mesozoic plants, including cycads. Dinosaurs have been proposed as key dispersers of cycad seeds during the Mesozoic, and temporal variation in cycad diversity and abundance has been linked to dinosaur faunal changes. Here we assess the evidence for proposed hypotheses of trophic and evolutionary interactions between these two groups using diversity analyses, a new database of Cretaceous dinosaur and plant co-occurrence data, and a geographical information system (GIS) as a visualisation tool. Phylogenetic evidence suggests that the origins of several key biological properties of cycads (e.g. toxins, bright-coloured seeds) likely predated the origin of dinosaurs. Direct evidence of dinosaur-cycad interactions is lacking, but evidence from extant ecosystems suggests that dinosaurs may plausibly have acted as seed dispersers for cycads, although it is likely that other vertebrate groups (e.g. birds, early mammals) also played a role. Although the Late Triassic radiations of dinosaurs and cycads appear to have been approximately contemporaneous, few significant changes in dinosaur faunas coincide with the late Early Cretaceous cycad decline. No significant spatiotemporal associations between particular dinosaur groups and cycads can be identified - GIS visualisation reveals disparities between the spatiotemporal distributions of some dinosaur groups (e.g. sauropodomorphs) and cycads that are inconsistent with co-evolutionary hypotheses. The available data provide no unequivocal support for any of the proposed co-evolutionary interactions between cycads and herbivorous dinosaurs

  6. The origin and early radiation of dinosaurs

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    Brusatte, Stephen L.; Nesbitt, Sterling J.; Irmis, Randall B.; Butler, Richard J.; Benton, Michael J.; Norell, Mark A.

    2010-07-01

    Dinosaurs were remarkably successful during the Mesozoic and one subgroup, birds, remain an important component of modern ecosystems. Although the extinction of non-avian dinosaurs at the end of the Cretaceous has been the subject of intense debate, comparatively little attention has been given to the origin and early evolution of dinosaurs during the Late Triassic and Early Jurassic, one of the most important evolutionary radiations in earth history. Our understanding of this keystone event has dramatically changed over the past 25 years, thanks to an influx of new fossil discoveries, reinterpretations of long-ignored specimens, and quantitative macroevolutionary analyses that synthesize anatomical and geological data. Here we provide an overview of the first 50 million years of dinosaur history, with a focus on the large-scale patterns that characterize the ascent of dinosaurs from a small, almost marginal group of reptiles in the Late Triassic to the preeminent terrestrial vertebrates of the Jurassic and Cretaceous. We provide both a biological and geological background for early dinosaur history. Dinosaurs are deeply nested among the archosaurian reptiles, diagnosed by only a small number of characters, and are subdivided into a number of major lineages. The first unequivocal dinosaurs are known from the late Carnian of South America, but the presence of their sister group in the Middle Triassic implies that dinosaurs possibly originated much earlier. The three major dinosaur lineages, theropods, sauropodomorphs, and ornithischians, are all known from the Triassic, when continents were joined into the supercontinent Pangaea and global climates were hot and arid. Although many researchers have long suggested that dinosaurs outcompeted other reptile groups during the Triassic, we argue that the ascent of dinosaurs was more of a matter of contingency and opportunism. Dinosaurs were overshadowed in most Late Triassic ecosystems by crocodile-line archosaurs and

  7. Mesozoic dinosaurs from Brazil and their biogeographic implications

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    Jonathas S. Bittencourt

    2011-03-01

    Full Text Available The record of dinosaur body-fossils in the Brazilian Mesozoic is restricted to the Triassic of Rio Grande do Sul and Cretaceous of various parts of the country. This includes 21 named species, two of which were regarded as nomina dubia, and 19 consensually assigned to Dinosauria. Additional eight supraspecific taxa have been identified based on fragmentary specimens and numerous dinosaur footprints known in Brazil. In fact, most Brazilian specimens related to dinosaurs are composed of isolated teeth and vertebrae. Despite the increase of fieldwork during the last decade, there are still no dinosaur body-fossils of Jurassic age and the evidence of ornithischians in Brazil is very limited. Dinosaur faunas from this country are generally correlated with those from other parts of Gondwana throughout the Mesozoic. During the Late Triassic, there is a close correspondence to Argentina and other south-Pangaea areas. Mid-Cretaceous faunas of northeastern Brazil resemble those of coeval deposits of North Africa and Argentina. Southern hemisphere spinosaurids are restricted to Africa and Brazil, whereas abelisaurids are still unknown in the Early Cretaceous of the latter. Late Cretaceous dinosaur assemblages of south-central Brazil are endemic only to genus or, more conspicuously, to species level, sharing closely related taxa with Argentina, Madagascar, Indo-Pakistan and, to a lesser degree, continental Africa.O registro osteológico de dinossauros no Mesozóico brasileiro está restrito a rochas triássicas do Rio Grande do Sul e estratos cretáceos de várias partes do país. Isto inclui 21 espécies nominais, sendo duas referidas como nomina dubia, e 19 consensualmente classificadas como dinossauros. Oito táxons supraespecíficos adicionais baseados em material fragmentado e diversas pegadas são conhecidos no Brasil. De fato, a maior parte dos espécimes é composta de dentes isolados e vértebras. Apesar do aumento em trabalhos de campo na última

  8. Higher-order phylogeny of modern birds (Theropoda, Aves: Neornithes) based on comparative anatomy. II. Analysis and discussion

    Science.gov (United States)

    LIVEZEY, BRADLEY C; ZUSI, RICHARD L

    2007-01-01

    In recent years, avian systematics has been characterized by a diminished reliance on morphological cladistics of modern taxa, intensive palaeornithogical research stimulated by new discoveries and an inundation by analyses based on DNA sequences. Unfortunately, in contrast to significant insights into basal origins, the broad picture of neornithine phylogeny remains largely unresolved. Morphological studies have emphasized characters of use in palaeontological contexts. Molecular studies, following disillusionment with the pioneering, but non-cladistic, work of Sibley and Ahlquist, have differed markedly from each other and from morphological works in both methods and findings. Consequently, at the turn of the millennium, points of robust agreement among schools concerning higher-order neornithine phylogeny have been limited to the two basalmost and several mid-level, primary groups. This paper describes a phylogenetic (cladistic) analysis of 150 taxa of Neornithes, including exemplars from all non-passeriform families, and subordinal representatives of Passeriformes. Thirty-five outgroup taxa encompassing Crocodylia, predominately theropod Dinosauria, and selected Mesozoic birds were used to root the trees. Based on study of specimens and the literature, 2954 morphological characters were defined; these characters have been described in a companion work, approximately one-third of which were multistate (i.e. comprised at least three states), and states within more than one-half of these multistate characters were ordered for analysis. Complete heuristic searches using 10 000 random-addition replicates recovered a total solution set of 97 well-resolved, most-parsimonious trees (MPTs). The set of MPTs was confirmed by an expanded heuristic search based on 10 000 random-addition replicates and a full ratchet-augmented exploration to ascertain global optima. A strict consensus tree of MPTs included only six trichotomies, i.e. nodes differing topologically among MPTs