Wednesday, November 23, 2016

[Paleontology • 2015] The Cranial Morphology of the Temnospondyl Australerpeton cosgriffi (Tetrapoda: Stereospondyli) from the Middle–Late Permian of Paraná Basin and the Phylogenetic Relationships of Rhinesuchidae


  Australerpeton cosgriffi in its environment (Middle–Late Permian [260 million years ago], Rio do Rasto Formation, Paraná Basin, Brazil)
Reconstruction by Rodolfo Nogueira.

DOI:  
10.1111/zoj.12339 
  
Abstract
Stereospondyls are a diverse and morphologically distinctive clade of basal tetrapods that rapidly reached a global distribution and high abundance during the Early Triassic. Yet, the first stereospondyls appeared in the Middle–Late Permian of Gondwana, mostly represented by Rhinesuchidae. Australerpeton cosgriffi is a long-snouted representative of the group and one of the most complete temnospondyls known from the Permian of South America. The elements attributed to Au. cosgriffi were recovered from the Middle-Late Permian deposits of the Rio do Rasto Formation (Paraná Basin), in the Serra do Cadeado area of Brazil. Here, we review the cranial anatomy of the species, providing a comparative redescription, new anatomical data and previously unrecognized characters. Australerpeton cosgriffi is nested within Rhinesuchidae based on the anatomy of the tympanic cavity, but its long-snouted condition is unique amongst rhinesuchids. Based on the recovered information and new morphological data, the systematic position of Au. cosgriffi was assessed using a new matrix of 221 characters; of which 196 were selected from previous studies and the remaining are newly proposed. The results show Rhinesuchidae divided into Rhinesuchinae and Australerpetinae. A unique tympanic cavity formed by a well posteroventrally projected tabular horn, stapedial groove, well-developed oblique crest on the pterygoid, and a dorsal pterygoid crest (new term) characterizes the ear region of Rhinesuchidae. Australerpeton cosgriffi is the only undisputed Rhinesuchidae record outside southern Africa and the first long-snouted Stereospondyli, and thus is useful in helping to understand the diversification of the stereospondyls during the Middle/Late Permian of Gondwana.

Keywords: Gondwana; long-snouted rhinesuchid; Palaeozoic; phylogenetics; Rio do Rasto Formation; systematics; Temnospondyli; tympanic cavity


Estevan Eltink, Eliseu V. Dias, Sérgio Dias-da-Silva, Cesar L. Schultz and Max C. Langer. 2015. The Cranial Morphology of the Temnospondyl Australerpeton cosgriffi (Tetrapoda: Stereospondyli) from the Middle–Late Permian of Paraná Basin and the Phylogenetic Relationships of Rhinesuchidae.  Zoological Journal of the Linnean Society. 176(4);   835–860.  DOI: 10.1111/zoj.12339

Paleontologists describe giant amphibian that lived 260 million years ago http://agencia.fapesp.br/paleontologists_describe_giant_amphibian_that_lived_260_million_years_ago/22285/

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