Full Text Available The end-Permian biotic crisis (~252.5 Ma represents the most severe extinction event in Earth's history. This paper investigates diversity patterns in Anomodontia, an extinct group of therapsid synapsids ('mammal-like reptiles', through time and in particular across this event. As herbivores and the dominant terrestrial tetrapods of their time, anomodonts play a central role in assessing the impact of the end-Permian extinction on terrestrial ecosystems. Taxonomic diversity analysis reveals that anomodonts experienced three distinct phases of diversification interrupted by the same number of extinctions, i.e. an end-Guadalupian, an end-Permian, and a mid-Triassic extinction. A positive correlation between the number of taxa and the number of formations per time interval shows that anomodont diversity is biased by the Permian-Triassic terrestrial rock record. Normalized diversity curves indicate that anomodont richness continuously declines from the Middle Permian to the Late Triassic, but also reveals all three extinction events. Taxonomic rates (origination and extinction indicate that the end-Guadalupian and end-Permian extinctions were driven by increased rates of extinction as well as low origination rates. However, this pattern is not evident at the final decline of anomodont diversity during the Middle Triassic. Therefore, it remains unclear whether the Middle Triassic extinction represents a gradual or abrupt event that is unique to anomodonts or more common among terrestrial tetrapods. The end-Permian extinction represents the most distinct event in terms of decline in anomodont richness and turnover rates.
Fucose is a monosaccharide that plays several immunological roles. This study investigated the comparative biosynthesis and cellular biodistribution of fucose residues in some tissues of tetrapoda representatives using lectin histochemistry. In this study, the mouse was used as a representative for mammalian, pigeon for avian, lizard for reptilian, and toad for amphibians. The localization of the fucose residues was seen in several cell types of mice ileum, such as villi microfold (M) cells, goblet cells, some of intestinal crypts cells, and lamina propria cells. In other tetrapoda representatives, fucose was only seen in M cells of lizard ileum and some cells of villi lamina propria of pigeon, lizard, and toad. It was also observed in the pancreatic acinar cells of the mouse and some cell aggregations of pancreatic parenchyma of the lizard. Contrarily, it was not seen either in pigeon or in toad pancreases parenchyma. Spleen of all animals showed the fucose residues in some splenic cells in the red pulp only, barring the white pulp. The liver parenchyma of all tetrapoda representatives hadn't fucose residues. The fucose cellular biodistribution in some cells of tetrapoda representatives differed based on the cell type. In the mouse, it was highly seen in the apical cytoplasm of the villi M cells as well as in the cup-like part of goblet cells. In addition, it was seen as "rings" in the granule membranes of the Ulex europeaus agglutinin I (UEAI(+)) cells in the intestinal crypts cells. Furthermore, the UEAI(+) cells in the lamina propria showed fucose granules in their cytoplasm. There is no clear evidence about the relation between the cellular biosynthesis of fucose residues and mucosal immune cells. The role of fucose residues in the pancreatic acinar cells are not well understood and need further investigations. In this study, fucose residues were synthesized in several types of cells in the mouse ileum, spleen and pancreas as compared with other tetrapoda. The
J. Francis Thackeray
Full Text Available Growth increments circa 0.02 mm in width have been observed in sectioned tusks of Diictodon from the Late Permian lower Beaufort succession of the South African Karoo, dated between about 260 and 245 million years ago. Mean growth increments show a decline from relatively high values in the Tropidostoma/Endothiodon Assemblage Zone, to lower values in the Aulacephalodon/Cistecephaluszone, declining still further in the Dicynodon lacerficeps/Whaitsia zone at the end of the Permian. These changes coincide with gradual changes in carbon isotope ratios measured from Diictodon tooth apatite. It is suggested that the decline in growth increments is related to environmental changes associated with a decline in primary production which contributed to the decline in abundance and ultimate extinction of Diictodon.
Brusatte, S. L.; Benton, M. J.; Desojo, J.B.; Langer, M.C.
Crown group Archosauria, which includes birds, dinosaurs, crocodylomorphs, and several extinct Mesozoic groups, is a primary division of the vertebrate tree of life. However, the higher-level phylogenetic relationships within Archosauria are poorly resolved and controversial, despite years of study. The phylogeny of crocodile-line archosaurs (Crurotarsi) is particularly contentious, and has been plagued by problematic taxon and character sampling. Recent discoveries and renewed focus on archo...
Woodruff, D Cary
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.
Full Text Available Transverse sections of the skull of the Permian therocephalian Glanosuchus sp. were studied with regard to the structures of the middle ear region. It is generally accepted that most of the skeletal elements of the mammalian middle ear are derived from the postdentary bones of the lower jaw. During synapsid evolution there is a gradual transition from a primitive amniote condition to derived mammalian condition; the latter is characterized by the decoupling of the remaining middle ear elements (angular, prearticular, articular from the dentary, which forms a secondary jaw articulation with the squamosal. Morganucodon from the Triassic-Jurassic boundary represents an evolutionary stage, where both jaw articulations are present in a coaxial position and where the primary joint is a Pready a fully effective sound transmitter. Therocephalians are considered to be a good representation of the transitory state of this evolutionary process; this may be especially true for primitive taxa such as the lycosuchid Glanosuchus, whose anatomy may represent the "groundplan" (ancestral morphotype of Lower to Middle Permian eutheriodonts. We studied a complete sectional series of a young specimen of Glanosuchus sp. prepared using the grind-and peel-technique. This showed that the reflected lamina of Glanosuchus is in major parts an extremely thin bony plate, which is best interpreted as a sound-receiving element overlying an air-filled recessus of the pharynx. In this specimen, the vestibular foramen and the stapes are preserved in situ; it is likely, however, that both structures were framed by cartilage which fixed the anular ligament. Both the stapes and the quadrate process of the pterygoid are in direct contact with the quadrate. Comparison of the area of the reflected lamina and the vestibular foramen shows that impedance matching was still very ineffective in Therocephalia when compared to extant mammals. In dieser Arbeit wurden Transversalschnitte des Schädels von dem Therocephalen Glanosuchus sp. im Hinblick auf die Anatomie der Mittelohrregion untersucht. Allgemein wird angenommen, dass die meisten Skelettelemente des Mittelohres der Säuger aus den postdentalen Knochen des Unterkiefers hervorgegangen sind. Der abgeleitete Zustand des Säuger-Mittelohres entstand demnach durch graduelle Abwandlung der ursprünglichen Amniotenkonstruktion. Der abgeleitete Zustand besteht darin, dass u. a. die drei postdentalen Elemente Angulare, Präartikulare und Artikulare aus dem Verband des Unterkiefers herausgelöst wurden, wobei das Dentale nun das Kiefergelenk mit dem Squamosum bildet. In der permotriassischen Gattung Morganucodon existieren beide Kiefergelenke nebeneinander, obwohl das primäre Kiefergelenk bereits die impedanzwandelnde Funktion übernommen hatte. Die Therocephalen sind ein weiteres Beispiel für eine solche evolutionäre Zwischenstellung, und unter diesen ist die ursprüngliche Gattung Glanosuchus besonders interessant. Sie gilt als beispielhaft für den Zustand unter- bis mittelpermischer Eutheriodonten. In der vorliegenden Arbeit untersuchten wir eine vollständige Schnittserie ("Grind-and-peel-Methode" eines juvenilen Glanosuchus sp. Die Lamina reflexa des untersuchten Stückes bildet eine sehr dünne Knochenlamelle, die sich am ehesten als schallübertragendes Element deuten läßt, das eine luftgefüllte Ausstülpung des Pharynx nach außen hin abschloss. Der Stapes und die Fenestra vestibuli des untersuchten Exemplares sind in situ erhalten, doch ist aufgrund fehlender Knochenränder wahrscheinlich, dass beide Strukturen sich knorpelig fortsetzten und durch ein Anularligament verbunden waren. Sowohl der Stapes als auch der Quadratfortsatz des Pterygoids hatten unmittelbaren Kontakt mit dem Quadratum. Das Flächenverhältnis zwischen der Lamina reflexa und der Fenestra vestibuli bei Glanosuchus laßt auf eine noch nicht sehr effektive Schallübertragung schließen. doi:10.1002/mmng.20020050119
Tam, Janice K V; Lau, Kwan-Wa; Lee, Leo T O; Chu, Jessica Y S; Ng, Kwong-Man; Fournier, Alain; Vaudry, Hubert; Chow, Billy K C
At present, secretin and its receptor have only been identified in mammals, and the origin of this ligand-receptor pair in early vertebrates is unclear. In addition, the elusive similarities of secretin and orexin in terms of both structures and functions suggest a common ancestral origin early in the vertebrate lineage. In this article, with the cloning and functional characterization of secretin receptors from lungfish and X. laevis as well as frog (X. laevis and Rana rugulosa) secretins, we provide evidence that the secretin ligand-receptor pair has already diverged and become highly specific by the emergence of tetrapods. The secretin receptor-like sequence cloned from lungfish indicates that the secretin receptor was descended from a VPAC-like receptor prior the advent of sarcopterygians. To clarify the controversial relationship of secretin and orexin, orexin type-2 receptor was cloned from X. laevis. We demonstrated that, in frog, secretin and orexin could activate their mutual receptors, indicating their coordinated complementary role in mediating physiological processes in non-mammalian vertebrates. However, among the peptides in the secretin/glucagon superfamily, secretin was found to be the only peptide that could activate the orexin receptor. We therefore hypothesize that secretin and orexin are of different ancestral origins early in the vertebrate lineage. PMID:21559418
Janice K V Tam
Full Text Available At present, secretin and its receptor have only been identified in mammals, and the origin of this ligand-receptor pair in early vertebrates is unclear. In addition, the elusive similarities of secretin and orexin in terms of both structures and functions suggest a common ancestral origin early in the vertebrate lineage. In this article, with the cloning and functional characterization of secretin receptors from lungfish and X. laevis as well as frog (X. laevis and Rana rugulosa secretins, we provide evidence that the secretin ligand-receptor pair has already diverged and become highly specific by the emergence of tetrapods. The secretin receptor-like sequence cloned from lungfish indicates that the secretin receptor was descended from a VPAC-like receptor prior the advent of sarcopterygians. To clarify the controversial relationship of secretin and orexin, orexin type-2 receptor was cloned from X. laevis. We demonstrated that, in frog, secretin and orexin could activate their mutual receptors, indicating their coordinated complementary role in mediating physiological processes in non-mammalian vertebrates. However, among the peptides in the secretin/glucagon superfamily, secretin was found to be the only peptide that could activate the orexin receptor. We therefore hypothesize that secretin and orexin are of different ancestral origins early in the vertebrate lineage.
Soares, Marina Bento; Schwanke, Cibele
We describe two new cynodonts from the early Late Triassic of southern Brazil. One taxon, Bonacynodon schultzi gen. et sp. nov., comes from the lower Carnian Dinodontosaurus AZ, being correlated with the faunal association at the upper half of the lower member of the Chañares Formation (Ischigualasto-Villa Unión Basin, Argentina). Phylogenetically, Bonacynodon is a closer relative to Probainognathus jenseni than to any other probainognathian, bearing conspicuous canines with a denticulate distal margin. The other new taxon is Santacruzgnathus abdalai gen. et sp. nov. from the Carnian Santacruzodon AZ. Although based exclusively on a partial lower jaw, it represents a probainognathian close to Prozostrodon from the Hyperodapedon AZ and to Brasilodon, Brasilitherium and Botucaraitherium from the Riograndia AZ. The two new cynodonts and the phylogenetic hypothesis presented herein indicate the degree to which our knowledge on probainognathian cynodonts is incomplete and also the relevance of the South American fossil record for understanding their evolutionary significance. The taxonomic diversity and abundance of probainognathians from Brazil and Argentina will form the basis of deep and complex studies to address the evolutionary transformations of cynodonts leading to mammals. PMID:27706191
Roderick Nigel Finn
Full Text Available A major physiological barrier for aquatic organisms adapting to terrestrial life is dessication in the aerial environment. This barrier was nevertheless overcome by the Devonian ancestors of extant Tetrapoda, but the origin of specific molecular mechanisms that solved this water problem remains largely unknown. Here we show that an ancient aquaporin gene cluster evolved specifically in the sarcopterygian lineage, and subsequently diverged into paralogous forms of AQP2, -5, or -6 to mediate water conservation in extant Tetrapoda. To determine the origin of these apomorphic genomic traits, we combined aquaporin sequencing from jawless and jawed vertebrates with broad taxon assembly of >2,000 transcripts amongst 131 deuterostome genomes and developed a model based upon Bayesian inference that traces their convergent roots to stem subfamilies in basal Metazoa and Prokaryota. This approach uncovered an unexpected diversity of aquaporins in every lineage investigated, and revealed that the vertebrate superfamily consists of 17 classes of aquaporins (Aqp0 - Aqp16. The oldest orthologs associated with water conservation in modern Tetrapoda are traced to a cluster of three aqp2-like genes in Actinistia that likely arose >500 Ma through duplication of an aqp0-like gene present in a jawless ancestor. In sea lamprey, we show that aqp0 first arose in a protocluster comprised of a novel aqp14 paralog and a fused aqp01 gene. To corroborate these findings, we conducted phylogenetic analyses of five syntenic nuclear receptor subfamilies, which, together with observations of extensive genome rearrangements, support the coincident loss of ancestral aqp2-like orthologs in Actinopterygii. We thus conclude that the divergence of sarcopterygian-specific aquaporin gene clusters was permissive for the evolution of water conservation mechanisms that facilitated tetrapod terrestrial adaptation.
A. Arandas Rêgo
Full Text Available Foram estudados os Cephalobaenidae (Pentastomida, depositados na coleção helmintológica do Instituto Oswaldo Cruz e na coleção de parasitologia do Instituto Butantan. São redescritas e discutidas as espécies, Cephalobaena tetrapoda, C. freitasi, C. giglioli, Raillietiella furcocerca e Mahafaliella venteli. Esses parasitas foram coletados dos répteis: Lachesis sp., Drymarchon c. corais, Xenodon merremii, Crotatus terrificus, Amphisbaena sp., Tropidurus torquatus, Bothrops atrox, Mabuya punctata e de Bufo paracnemis (anfíbio.In this work the author studies Cephalobaenidae parasites using specimens from the helminthological collection of the Oswaldo Cruz and Butantan Institutes. This material was collected from Lachesis sp., Drymarchon corais, Xenodon merremii, Crotalus terrificus, Amphisbaena sp., Tropidurus torquatus, Bothrops atrox, Mabuya punctata (Reptilia and Bufo paracnemis (Amphibia. The species studied are Cephalobaena tetrapoda Heymons, 1922, Cephalobaena giglioli (Hett, 1924 comb. n., Cephalobaena freitasi (Motta & Gomes, 1968 comb. n., Raillietiella furcocerca (Diesing, 1836 and Mahafaliella venteli (Motta, 1965. C. recurvocauda becomes a synonym of C. tetrapoda and as do the specimens that Motta called erronously R. furcocerca. Raillietiella giglioli is changed to Cephalobaena giglioli (Hett, 1924 comb. n. The author describes here the male of C. giglioli for the first time. Travassostulida freitasi and T. acutiacanthus enter in synonymy with C. freitasi, and T. acutiacanthus is considered to be a subspecies of C. freitasi. Raillietiella gomesi becomes a synonym of R. furcocerca. The author discusses Mahafaliella venteli, and also questions the validity of the genus Gretillaria proposed by Motta for some species of Raillietiella. The latter is considered a synonym of Raillietiella.
Almeida, W O; Vasconcellos, A; Lopes, S G; Freire, E M X
This study aimed to evaluate the infection rates of snakes by pentastomids in the semi-arid region of Brazil. Fifteen snakes (four Micrurus ibiboboca (Merrem, 1820) and eleven Philodryas nattereri Steindachner, 1870) were collected between January and April of 2005, in the municipality of Crato (07 degrees 14' S and 39 degrees 24' W), State of Ceará, Brazil. Laboratorial analysis of the respiratory tracts of the sampled snakes indicated differences in host infection rates: four individuals of P. nattereri (36.4%) were infected by Cephalobaena tetrapoda Heymons, 1922 (mean infection intensity 1.5 +/- 0.28, 1-2) and three specimens (27.3%) by Raillietiella furcocerca (Diesing, 1863) (2.3 +/- 1.32, 1-5). Only one individual of M. ibiboboca (25%) was infected by a non-identified species of Raillietiella sp. These are the first data on pentastomid infection in snakes in Northeastern Brazil and both snake species comprise new host records for the pentastomids. The results also indicate that the generalist parasites C. tetrapoda and R. furcocerca share their definitive hosts. PMID:18278332
Hallström, Björn M; Janke, Axel
The relationship between the Chondrichthyes (cartilaginous fishes), the Actinopterygii (ray-finned fishes), and the piscine Sarcopterygii (lobe-finned fishes) and how the Tetrapoda (four-limbed terrestrial vertebrates) are related to these has been a contentious issue for more than a century. A general consensus about the relationship of these vertebrate clades has gradually emerged among morphologists, but no molecular study has yet provided conclusive evidence for any specific hypothesis. In order to examine these relationships on the basis of more extensive sequence data, we have produced almost 1,000,000 bp of expressed sequence tags (ESTs) from the African marbled lungfish, Protopterus aethiopicus. This new data set yielded 771 transcribed nuclear sequences that had not been previously described. The lungfish EST sequences were combined with EST data from two cartilaginous fishes and whole genome data from an agnathan, four ray-finned fishes, and four tetrapods. Phylogenomic analysis of these data yielded, for the first time, significant maximum likelihood support for a traditional gnathostome tree with a split between the Chondrichthyes and remaining (bone) gnathostomes. Also, the sister group relationship between Dipnoi (lungfishes) and Tetrapoda received conclusive support. Previously proposed hypotheses, such as the monophyly of fishes, could be rejected significantly. The divergence time between lungfishes and tetrapods was estimated to 382-388 Ma by the current data set and six calibration points. PMID:19029191
Fischer, Martin S.
Der Bewegungsapparat bestimmt die Form des Wirbeltierkörpers. So lässt sich z. B. aus der Gestalt eines Fisches auf seine bevorzugt e Schwimmweise schließen (S. 61). Bei den aquatisch en Schädeltieren dominiert die Fortbewegung mit axialem Antrieb; bei den meisten Tetrapoda findet sich eine Kombination aus axialem Antrieb und Bewegung durch Gliedmaßen. Selbst beim höchst spezialisierten Gang, der bipeden Bewegung des Menschen, sind Torsionsbewegungen des Rumpfes noch maßgeblich und bestimmen auch die Grundform des menschlichen Körpers (z. B. die Taille). Obwohl die verschiedenen Antriebsmechanismen eine funktionelle Einheit bilden, werden im Folgenden das Axialskelett sowie der Schulter- und Beckengürtel mit den zugehörigen Extremitäten getrennt besprochen.
Almeida, W O; Guedes, T B; Freire, E M X; Vasconcellos, A
The relationship between pentastomids and two Colubridae species, Phillodryas nattereri Steindachner, 1870 and Oxybelis aeneus (Wagler, 1824), were investigated in the federal government's reserve Estação Ecológica do Seridó (ESEC, Seridó) situated at lat 6 degrees 35'-40' S and long 37 degrees 15'-20 W in the municipality of Serra Negra do Norte, state of Rio Grande do Norte, Northeast Brazil and run by IBAMA (the Brazilian Institute for the Environment and Natural Resources). Throughout 2005, 26 specimens of snakes, 13 of P. nattereri and 13 of O. aeneus were collected. After anatomical dissection and laboratorial examination of the snakes respiratory tracts, P. nattereri was found to be parasitized by two species of pentastomids: Cephalobaena tetrapoda Heymons, 1922 with a prevalence of 30.8% and a mean intensity of infection of 51.5 +/- 32.7 (range 3-147), and Raillietiella furcocerca (Diesing, 1863) which had a prevalence of 7.7% and a mean intensity of infection of 1.0. Only one female of O. aeneus was found to be infected by C. tetrapoda, with a prevalence of 7.7% and mean intensity of infection of 2.0. There was no significant relationship between size of snout-vent length (SVL) and intensity of infection in the specimens investigated here. The two individuals of P. nattereri infected by more than 40 specimens of pentastomids had their lungs completely infected including the pulmonary peritoneum and trachea. It is noteworthy that the hosts had their lung tissues partially destroyed with apparent haemorrhage, and the trabecular structure of their lungs was also destroyed. The contrasting rates of infection estimated here may be related to differences in foraging strategies, in diet, and habitat selection carried out by individuals of P. nattereri and O. aeneus. PMID:18470397
Almeida, W O; Guedes, T B; Freire, E M X; Vasconcellos, A
The relationship between pentastomids and two Colubridae species, Phillodryas nattereri Steindachner, 1870 and Oxybelis aeneus (Wagler, 1824), were investigated in the federal government's reserve Estação Ecológica do Seridó (ESEC, Seridó) situated at lat 6 degrees 35'-40' S and long 37 degrees 15'-20 W in the municipality of Serra Negra do Norte, state of Rio Grande do Norte, Northeast Brazil and run by IBAMA (the Brazilian Institute for the Environment and Natural Resources). Throughout 2005, 26 specimens of snakes, 13 of P. nattereri and 13 of O. aeneus were collected. After anatomical dissection and laboratorial examination of the snakes respiratory tracts, P. nattereri was found to be parasitized by two species of pentastomids: Cephalobaena tetrapoda Heymons, 1922 with a prevalence of 30.8% and a mean intensity of infection of 51.5 +/- 32.7 (range 3-147), and Raillietiella furcocerca (Diesing, 1863) which had a prevalence of 7.7% and a mean intensity of infection of 1.0. Only one female of O. aeneus was found to be infected by C. tetrapoda, with a prevalence of 7.7% and mean intensity of infection of 2.0. There was no significant relationship between size of snout-vent length (SVL) and intensity of infection in the specimens investigated here. The two individuals of P. nattereri infected by more than 40 specimens of pentastomids had their lungs completely infected including the pulmonary peritoneum and trachea. It is noteworthy that the hosts had their lung tissues partially destroyed with apparent haemorrhage, and the trabecular structure of their lungs was also destroyed. The contrasting rates of infection estimated here may be related to differences in foraging strategies, in diet, and habitat selection carried out by individuals of P. nattereri and O. aeneus.
Full Text Available Dicynodontia represent the most diverse tetrapod group during the Late Permian. They survived the Permo-Triassic extinction and are central to understanding Permo-Triassic terrestrial ecosystems. Although extensively studied, several aspects of dicynodont paleobiology such as, neuroanatomy, inner ear morphology and internal cranial anatomy remain obscure. Here we describe a new dicynodont (Therapsida, Anomodontia from northern Mozambique: Niassodon mfumukasi gen. et sp. nov. The holotype ML1620 was collected from the Late Permian K5 formation, Metangula Graben, Niassa Province northern Mozambique, an almost completely unexplored basin and country for vertebrate paleontology. Synchrotron radiation based micro-computed tomography (SRµCT, combined with a phylogenetic analysis, demonstrates a set of characters shared with Emydopoidea. All individual bones were digitally segmented allowing a 3D visualization of each element. In addition, we reconstructed the osseous labyrinth, endocast, cranial nerves and vasculature. The brain is narrow and the cerebellum is broader than the forebrain, resembling the conservative, "reptilian-grade" morphology of other non-mammalian therapsids, but the enlarged paraflocculi occupy the same relative volume as in birds. The orientation of the horizontal semicircular canals indicates a slightly more dorsally tilted head posture than previously assumed in other dicynodonts. In addition, synchrotron data shows a secondary center of ossification in the femur. Thus ML1620 represents, to our knowledge, the oldest fossil evidence of a secondary center of ossification, pushing back the evolutionary origins of this feature. The fact that the specimen represents a new species indicates that the Late Permian tetrapod fauna of east Africa is still incompletely known.
Durand, J. F.
Over more than two centuries, Africa has been an important source of knowledge with regard to the origins, evolution and distribution of important animal taxa. Not only did Africa south of the Sahara contain a second zoogeographical region virtually unknown four centuries ago, but also gave the world the first insight into the palaeontological wealth and the existence of Gondwana. The section on Agnatha includes a discussion on conodonts from South Africa, considered to be the some of the oldest and best-preserved vertebrate fossils in the world. The section on the Gnathostomata includes a very brief overview of the most important fish taxa from the Palaeozoic to Mesozoic of Africa. The section on the Tetrapoda includes an overview of the major taxa found in the fossil record of the Palaeozoic and Mesozoic of Africa. The Permian and Triassic tetrapod fossils that indicate the evolution and radiation of the parareptiles, eureptiles and synapsids are highlighted. The most important vertebrate fossils from Africa that contributed to our understanding of the radiation of evolutionary important groups such as the fish, tetrapods, tortoises, snakes, crocodiles, dinosaurs and mammals are discussed. The Jurassic and Cretaceous assemblages containing dinosaur and mammal remains, deposited after the break up of Gondwana, are discussed. Finally a perspective on the importance of Africa as fossil repository and the limitations of palaeontological endeavour in Africa is given.
Brainerd, Elizabeth L; Owerkowicz, Tomasz
In the evolution of aspiration breathing, the responsibility for lung ventilation gradually shifted from the hyobranchial to the axial musculoskeletal system, with axial muscles taking over exhalation first, at the base of Tetrapoda, and then inhalation as well at the base of Amniota. This shift from hyobranchial to axial breathing freed the tongue and head to adapt to more diverse feeding styles, but generated a mechanical conflict between costal ventilation and high-speed locomotion. Some "lizards" (non-serpentine squamates) have been shown to circumvent this speed-dependent axial constraint with accessory gular pumping during locomotion, and here we present a new survey of gular pumping behavior in the tuatara and 40 lizard species. We observed gular pumping behavior in 32 of the 40 lizards and in the tuatara, indicating that the ability to inflate the lungs by gular pumping is a shared-derived character for Lepidosauria. Gular pump breathing in lepidosaurs may be homologous with buccal pumping in amphibians, but non-ventilatory buccal oscillation and gular flutter have persisted throughout amniote evolution and gular pumping may have evolved independently by modification of buccal oscillation. In addition to gular pumping in some lizards, three other innovations have evolved repeatedly in the major amniote clades to circumvent the speed-dependent axial constraint: accessory inspiratory muscles (mammals, crocodylians and turtles), changing locomotor posture (mammals and birds) and respiratory-locomotor phase coupling to reduce the mechanical conflict between aspiration breathing and locomotion (mammals and birds).
Harris, Jerald D
At present, three different systems of anatomical nomenclature are available to researchers describing new tetrapod taxa: a nonstandardized traditional system erected in part by Sir Richard Owen and subsequently elaborated by Alfred Romer; a standardized system created for avians, the Nomina Anatomica Avium (NAA); and a standardized system for extant (crown-group) mammals, the Nomina Anatomica Veterinaria (NAV). Conserved homologous structures widely distributed within the Tetrapoda are often granted different names in each system. The recent shift toward a phylogenetic system based on homology requires a concomitant shift toward a single nomenclatural system also based on both evolutionary and functional morphological homology. Standardized terms employed in the NAA and NAV should be perpetuated as far as possible basally in their respective phylogenies. Thus, NAA terms apply to nonavian archosaurs (or even all diapsids) and NAV terms apply to noncrown-group mammals and more basal synapsids. Taxa equally distant from both avians and crown-group mammals may maintain the traditional nonstandardized terminology until a universal anatomical nomenclature for all tetrapods is constructed.
Full Text Available Since its usage by Darwin in 1859, the concept of ‘living fossil’ has undergone multiple definitions and has been much discussed and criticized. Soon after its discovery in 1938, the coelacanth Latimeria was regarded as the iconic example of a ‘living fossil’. Several morphological studies have shown that the coelacanth lineage (Actinistia has not displayed critical morphological transformation during its evolutionary history and molecular studies have revealed a low substitution rate for Latimeria, indicating a slow genetic evolution. This statement, however, has been recently questioned by arguing that the low substitution rate was not real, and that the slow morphological evolution of actinistians was not supported by paleontological evidence. The assessment of morphological transformation among three vertebrate lineages during a time interval of circa 400 million years shows that the morphological disparity of coelacanths is much more reduced than the morphological disparity of Actinopterygii and Tetrapoda. These results support the idea that living coelacanths are singular organisms among the living world.
Hanukoglu, Israel; Hanukoglu, Aaron
The epithelial sodium channel (ENaC) is composed of three homologous subunits and allows the flow of Na(+) ions across high resistance epithelia, maintaining body salt and water homeostasis. ENaC dependent reabsorption of Na(+) in the kidney tubules regulates extracellular fluid (ECF) volume and blood pressure by modulating osmolarity. In multi-ciliated cells, ENaC is located in cilia and plays an essential role in the regulation of epithelial surface liquid volume necessary for cilial transport of mucus and gametes in the respiratory and reproductive tracts respectively. The subunits that form ENaC (named as alpha, beta, gamma and delta, encoded by genes SCNN1A, SCNN1B, SCNN1G, and SCNN1D) are members of the ENaC/Degenerin superfamily. The earliest appearance of ENaC orthologs is in the genomes of the most ancient vertebrate taxon, Cyclostomata (jawless vertebrates) including lampreys, followed by earliest representatives of Gnathostomata (jawed vertebrates) including cartilaginous sharks. Among Euteleostomi (bony vertebrates), Actinopterygii (ray finned-fishes) branch has lost ENaC genes. Yet, most animals in the Sarcopterygii (lobe-finned fish) branch including Tetrapoda, amphibians and amniotes (lizards, crocodiles, birds, and mammals), have four ENaC paralogs. We compared the sequences of ENaC orthologs from 20 species and established criteria for the identification of ENaC orthologs and paralogs, and their distinction from other members of the ENaC/Degenerin superfamily, especially ASIC family. Differences between ENaCs and ASICs are summarized in view of their physiological functions and tissue distributions. Structural motifs that are conserved throughout vertebrate ENaCs are highlighted. We also present a comparative overview of the genotype-phenotype relationships in inherited diseases associated with ENaC mutations, including multisystem pseudohypoaldosteronism (PHA1B), Liddle syndrome, cystic fibrosis-like disease and essential hypertension. PMID
Meyer, A; Dolven, S I
Since the discovery of the coelacanth, Latimeria chalumnae, more than 50 years ago, paleontologists and comparative morphologists have debated whether coelacanths or lungfishes, two groups of lobe-finned fishes, are the closest living relatives of land vertebrates (Tetrapoda). Previously, Meyer and Wilson (1990) determined partial DNA sequences from two conservative mitochondrial genes and found support for a close relationship of lungfishes to tetrapods. We present additional DNA sequences from the 12S rRNA mitochondrial gene for three species of the two lineages of lungfishes that were not represented in the first study: Protopterus annectens and Protopterus aethiopicus from Africa and Neoceratodus forsteri (kindly provided by B. Hedges and L. Maxson) from Australia. This extended data set tends to group the two lepidosirenid lungfish lineages (Lepidosiren and Protopterus) with Neoceratodus as their sister group. All lungfishes seem to be more closely related to tetrapods than the coelacanth is. This result appears to rule out the possibility that the coelacanth lineage gave rise to land vertebrates. The common ancestor of lungfishes and tetrapods might have possessed multiple morphological traits that are shared by lungfishes and tetrapods [Meyer and Wilson (1990) listed 14 such traits]. Those traits that seem to link Latimeria and tetrapods are arguably due to convergent evolution or reversals and not to common descent. In this way, the molecular tree facilitates an evolutionary interpretation of the morphological differences among the living forms. We recommended that the extinct groups of lobe-finned fishes be placed onto the molecular tree that has lungfishes and not the coelacanth more closely related to tetrapods. The placement of fossils would help to further interpret the sequence of morphological events and innovations associated with the origin of tetrapods but appears to be problematic because the quality of fossils is not always high enough, and
Pestov, Nikolay B., E-mail: email@example.com [Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow 117871 (Russian Federation); Dmitriev, Ruslan I.; Kostina, Maria B. [Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow 117871 (Russian Federation); Korneenko, Tatyana V. [Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow 117871 (Russian Federation); Department of Physiology and Pharmacology, University of Toledo College of Medicine, 3000 Arlington Ave., Toledo, OH 43614 (United States); Shakhparonov, Mikhail I. [Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow 117871 (Russian Federation); Modyanov, Nikolai N., E-mail: firstname.lastname@example.org [Department of Physiology and Pharmacology, University of Toledo College of Medicine, 3000 Arlington Ave., Toledo, OH 43614 (United States)
Highlights: Black-Right-Pointing-Pointer Full-length secretory pathway Ca-ATPase (SPCA2) cloned from rat duodenum. Black-Right-Pointing-Pointer ATP2C2 gene (encoding SPCA2) exists only in genomes of Tetrapoda. Black-Right-Pointing-Pointer Rat and pig SPCA2 are expressed in intestines, lung and some secretory glands. Black-Right-Pointing-Pointer Subcellular localization of SPCA2 may depend on tissue type. Black-Right-Pointing-Pointer In rat duodenum, SPCA2 is localized in plasma membrane-associated compartments. -- Abstract: Secretory pathway Ca-ATPases are less characterized mammalian calcium pumps than plasma membrane Ca-ATPases and sarco-endoplasmic reticulum Ca-ATPases. Here we report analysis of molecular evolution, alternative splicing, tissue-specific expression and subcellular localization of the second isoform of the secretory pathway Ca-ATPase (SPCA2), the product of the ATP2C2 gene. The primary structure of SPCA2 from rat duodenum deduced from full-length transcript contains 944 amino acid residues, and exhibits 65% sequence identity with known SPCA1. The rat SPCA2 sequence is also highly homologous to putative human protein KIAA0703, however, the latter seems to have an aberrant N-terminus originating from intron 2. The tissue-specificity of SPCA2 expression is different from ubiquitous SPCA1. Rat SPCA2 transcripts were detected predominantly in gastrointestinal tract, lung, trachea, lactating mammary gland, skin and preputial gland. In the newborn pig, the expression profile is very similar with one remarkable exception: porcine bulbourethral gland gave the strongest signal. Upon overexpression in cultured cells, SPCA2 shows an intracellular distribution with remarkable enrichment in Golgi. However, in vivo SPCA2 may be localized in compartments that differ among various tissues: it is intracellular in epidermis, but enriched in plasma membranes of the intestinal epithelium. Analysis of SPCA2 sequences from various vertebrate species argue that ATP2C2
Full Text Available São conhecidos, com segurança, três diferentestáxons de dicinodontes para o Triássico doRio Grande do Sul, representados pelos gênerosStahleckeria Huene, 1934, Dinodontosaurus Romer,1943 e Jachaleria Bonaparte, 1970. Dinodontosauruse Stahleckeria coexistiram temporalmente naCenozona de Therapsida (Mesotriássico, Ladinianoenquanto Jachaleria era a única forma de dicinodontena Cenozona de Mamaliamorpha (Neotriássico,Eonoriano?. Dos três, apenas Dinodontosaurusapresenta o par de presas caniniformes que caracterizao grupo, sendo as demais formas totalmenteedentadas, mas esta característica está mais provavelmentevinculada à ornamentação e não interferena discussão mecânica aqui proposta. A robustez dasmandíbulas e a eficiência da musculatura empregadano ciclo mastigatório podem ser reflexos do grau deprocessamento oral e da resistência do material a seringerido. Nesse sentido, os três taxa de dicinodontessupracitados foram comparados quanto às variaçõesda morfologia craniana, discutindo os modos comque estas afetam o comprimento das fibras muscularese os ângulos de inserção da musculatura nas mandíbulas,indicando a dimensão dos braços de alavancadas forças exercidas por esses músculos em relaçãoà articulação crânio-mandibular. Assim, pode-seter um quadro das vantagens mecânicas de diferentesarranjos musculares. Optou-se por realizar umaanálise da ação da mandíbula como um corpo livre,tratando todas as mandíbulas com o mesmo comprimento,a fim de que a dimensão do braço de alavancadas forças executadas pelos diferentes músculosseja um reflexo direto de suas vantagens mecânicas,quando comparados os mesmos músculos entre doisanimais. Quanto maior o braço de alavanca de umconjunto muscular de um animal em relação a outro,menor o esforço necessário para o primeiro executara ação. Utilizando como referência uma orientaçãohorizontal do palato e basicrânio, ao compararem-seos crânios dos tr