Academic literature on the topic 'Labyrinthodontia'

An amphibian trackway collected in minespoil from the Cross Mountain Formation in the Cumberland Mountains of East Tennessee represents the first known Middle Pennsylvanian (Westphalian) amphibian trackway from the southeastern United States. The tracks are impressed onto the upper surface of a bed of fine-grained, cross-laminated sandstone and siltstone, deposited in an upper delta plain environment.The trackway was made by an amphibian with a long glenoacetabular distance and low pace-angulation. The imprints show five digits on the pes and four on the manus. Average measurements for the trackway are: stride, 8.4 cm; pace angulation, 76.1° (manus), 63.1° (pes); track width, 5.5 cm (manus), 6.7 cm (pes); glenoacetabular distance, 16.7 cm. The manus impression averages 2.8 cm long by 3.1 cm wide, and the pes averages 3.8 cm long by 3.1 cm wide. A tail drag is conspicuous along the entire length of the trackway and has a minimum radius of curvature of 9 mm.The trackway is assigned to Matthewichnus caudifer n. ichnosp. on the basis of similarities to published material. The trackmaker was probably a temnospondyl labyrinthodont, considering the size of the animal (thus excluding lepospondyls) and the fact that it had a four-digit manus (thus excluding reptiles and anthracosaurian labyrinthodonts).

The origin of tetrapods from sarcopterygian fish in the Late Devonian is one of the best known major transitions in the history of vertebrates. Unfortunately, extensive gaps in the fossil record of the Lower Carboniferous and Triassic make it very difficult to establish the nature of relationships among Paleozoic tetrapods, or their specific affinities with modern amphibians. The major lineages of Paleozoic labyrinthodonts and lepospondyls are not adequately known until after a 20–30 m.y. gap in the Early Carboniferous fossil record, by which time they were highly divergent in anatomy, ways of life, and patterns of development. An even wider temporal and morphological gap separates modern amphibians from any plausible Permo-Carboniferous ancestors. The oldest known caecilian shows numerous synapomorphies with the lepospondyl microsaur Rhynchonkos. Adult anatomy and patterns of development in frogs and salamanders support their origin from different families of dissorophoid labyrinthodonts. The ancestry of amniotes apparently lies among very early anthracosaurs.

Les Temnospondyles forment un clade de Stégocéphales dont les données ontogénétiques sont les plus complètes au sein des Tétrapodes basaux. Dans le cadre d'une approche ontogénie/phylogénie, 12 espèces de Temnospondyles et une de Seymouriamorphe (premier extragroupe) ont été considérées. Trois stades développementaux (larvaire, juvénile et adulte) ont été mis en évidence d'après différents marqueurs anatomiques et ostéologiques [. . . ] et 182 caractères [. . . ] ont été décrits, codés et polaris ́es pour chacun de ces stades, en fonction du critère extragroupe puis ontogénétique (pour les formes adultes seulement). Au total, quatre matrices ont été construites. Dans un premier temps, ces matrices ont été traitées séparément et les arbres obtenus comparés ('systematic congruence'). Dans un deuxième temps, ces matrices ont été combinées ('total evidence'). L'analyse comparée a générée quatre arbres ('ontotrees') non congruents. L'analyse combinée a généré huit arbres dont les topologies rappellent celles des 'ontotrees'. Certains taxons ont des positions variables en fonction des arbres. Les caractères à l'origine des incongruences entre 'ontotrees' correspondent à certaines homoplasies des arbres combinés. Ces incongruences sont interprétées comme des hétérochronies du développement ou des erreurs possibles dans l'identification de formes larvaires. Les deux principaux types d'hétérochronies (paedomorphie et peramorphie) ont été ainsi avancées pour expliquer la diversification du groupe. Cette nouvelle méthode a des répercussions sur le mode et le milieu de vie des Stégocéphales. Une phylogénie globale et consensuelle indique en effet que la sortie des eaux a eu lieu au Carbonifère supérieur et non au Dévonien supérieur comme proposé antérieurement. Les temnospondyles sont sortis de l'eau au moins une fois au cours de l'évolution et cette transition se serait effectuée en eau douce. Enfin, l'euryhalinité de certains Stégocéphales, bien que physiologiquement non expliquée, aurait aussi joué un rôle non négligeable dans leur diversification.

O centro-leste do Estado de São Paulo expõe boa parte da seção neopaleozóica da Bacia do Paraná, com sedimentos do Grupo Tubarão (Subgrupo Itararé e Formação Tatuí) e o Grupo Passa Dois (formações Irati e Corumbataí). Na região entre Leme e Capivari e na região do Domo de Pitanga, entre Piracicaba e Ipeúna, a transição entre as formações Tatuí e Irati é caracterizada comumente por arenitos relativamente grossos e mal selecionados (arenitos com grânulos, arenitos conglomeráticos e conglomerados), abundantemente fossilíferos em contato abrupto com os folhelhos síltico-argilosos da Formação Irati. O presente trabalho concentrou-se no estudo de paleovertebrados paleozóicos aplicado à interpretação paleontológica, sedimentológica e estratigráfica da transição entre os grupos Tubarão e Passa Dois. O conteúdo fóssil identificado compreende escamas, dentes e partes ósseas de vários tipos de peixes, de água doce e salgada, e de possíveis tetrápodes. Os Chondrichthyes são representados por duas variedades de dentes cladodontes; vários tipos de dentes do Xenacanthiformes ?Pleuracanthus? albuquerquei Silva Santos, 1946; dentes de Orodontiformes; dentes de duas espécies de Petalodontiformes, a primeira, e mais comum, Itapyrodus punctatus Silva Santos, 1990 e a segunda, representada por um único exemplar, uma espécie indeterminada. O material ainda inclui um espinho de nadadeira dorsal de Ctenacanthiformes adulto e uma possível escama placóide. A fauna de Osteichthyes é a mais abundante, sendo composta de dentes e escamas ganóides de Paleonisciformes e escamas cosmóides de Actinistia. São observados grandes dentes labirintodontes (provenientes de tetrápodes primitivos e/ou? peixes Rhipidistia) e partes ósseas atribuídas a peixes e/ou possíveis anfíbios. Os fósseis estão normalmente dispersos e desarticulados e os elementos ósseos fragmentados e desgastados. Mesmo assim, foram encontrados dentes de animais continentais - labirintodontes e Xenacanthiformes, com diferentes tipos de preservação, o que indicaria uma influência fluvial. A mistura de elementos marinhos, como Petalodontes, e continentais sugere um caráter marinho costeiro com forte influência continental para a transição entre as unidades. Os estudos tafonômicos sugerem que a camada de estudo é um depósito residual, resultado direto do retrabalhamento por ondas. Portanto, a transição Tatuí - Irati faz parte da evolução deposicional da Formação Irati. Sugere-se que ela seja reconhecida como uma fácies basal local, de grande importância paleontológica e estratigráfica no centro-leste do Estado de São Paulo.
A good part of the Neopaleozoic section of the Paraná basin is well-exposed in central-east Sao Paulo, Brazil, represented by sedimentary rocks of the Tubarão Group (Itararé Subgroup and Tatuí Formation) and the Passa Dois Group (Irati and Corumbataí formations). Between Leme and Capivari and in the area of the Pitanga Dome, between Piracicaba and Ipeúna, the transition between the Tatuí and Irati formations commonly is characterized by abundantly fossiliferous, poorly sorted, relatively coarse sandstones (sandstones with granules, conglomeratic sandstones and conglomerate) in abrupt contact with silty shale of the Irati Formation. The present work concentrated on the study of Palaeozoic palaeovertebrates and their significance for paleontological, sedimentological and stratigraphical interpretations of the transition between the Tubarão and Passa Dois groups. The identified fossil content consists of scales, teeth and bony parts from several types of fish, from fresh and salt water, as well as from possible tetrapods. Chondrichthyes are represented by two varieties of cladodont teeth; several types of teeth of the xenacanth ?Pleuracanthus? albuquerquei Silva Santos, 1946; teeth of Orodontiformes; teeth of two species of Petalodontiformes, the first, and more common, Itapyrodus punctatus Silva Santos, 1990, and the other, represented by a single specimen, an unidentified species. The material also includes a fin spine of an adult Ctenacanthiformes and a possible placoid scale. The fauna of Osteichthyes is more abundant, being composed of teeth and ganoid scales of Paleonisciformes and cosmoid scales of Actinistia. Also observed are large labyrinthodont teeth (from primitive tetrapods and/or rhipidistid fish) and bony parts attributed to fish and/or possible amphibians. The fossils are usually disarticulated and dispersed and the bony elements fragmented and abraded. Even so, teeth of continental animals - labyrinthodonts and Xenacanthiformes, were found with different types of preservation, which is indicative of a fluvial influence. The mixture of marine elements, like petalodonts, and continental elements suggests a nearshore character with a strong continental influence for the transition between the units. Taphonomic studies suggest that the studied layer is a residual (lag) deposit that resulted directly from reworking by waves. Thus, the Tatuí - Irati transition is part of the depositional evolution of the early Irati Formation. It is therefore suggested that the transition be recognized as a local basal facies of this formation of great paleontological and stratigraphical importance in the central-eastern part of the state of Sao Paulo.

L’anatomie interne des crânes des stégocéphales Stanocephalosaurus (Temnospondyli), Laosuchus (Chroniosuchia) et Diplocaulus (Lepospondyli) a pu être révélée par l’utilisation de la tomographie à rayons X et a permis de mieux comprendre leur paléobiologie : 1) l’oreille moyenne de Stanocephalosaurus serait adaptée à la perception de sons dans le milieu subaquatique ; 2) des canaux sensoriels intra-osseux ont été identifiés chez Laosuchus. La morphologie endocrânienne a ensuite été utilisée dans une analyse phylogénétique portant sur les relations de parentés controversées entre stégocéphales et lissamphibiens. Cette analyse montre que la monophylie des lissamphibiens serait due à un phénomène d’attraction des longues branches, résultant de l’optimisation de la simplification crânienne, identifiée comme une convergence. Les morphologies de la boite crânienne, du stapes et du palais favorisent une origine diphylétique des lissamphibiens parmi les temnospondyles
The intracranial anatomy of the stegocephals Stanocephalosaurus (Temnospondyli), Laosuchus (Chroniosuchia) and Diplocaulus (Lepospondyli) has been revealed by X-rays tomography and allowed to better understand their paleobiology: 1) the middle ear of Stanocephalosaurus would be an underwater adapted hearing system; 2) intraosseous sensorial canals have been identified in Laosuchus. The endocranial morphology have been included in a phylogenetic analysis on the debated relationships between stegocephals and lissamphibians. This analysis shows that the monophyly of Lissamphibia may result from a long-branch attraction, due to the optimisation of the cranial simplification, here as identified convergent. The morphologies of braincase, stapes and palate favour a biphyletic origin of lissamphibians among temnospondyls