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Australia’s prehistoric ‘swamp king’: revision of the Plio-Pleistocene crocodylian genus Pallimnarchus de Vis, 1886

The crocodylian fossil record from the Cenozoic of Australasia is notable for its rich taxonomic diversity, and is primarily represented by members of the clade Mekosuchinae. Reports of crocodylian fossils from Australia date back to the late nineteenth century. In 1886, Charles Walter de Vis propos...

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Autores principales: Ristevski, Jorgo, Yates, Adam M., Price, Gilbert J., Molnar, Ralph E., Weisbecker, Vera, Salisbury, Steven W.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: PeerJ Inc. 2020
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7759136/
https://www.ncbi.nlm.nih.gov/pubmed/33391869
http://dx.doi.org/10.7717/peerj.10466
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author Ristevski, Jorgo
Yates, Adam M.
Price, Gilbert J.
Molnar, Ralph E.
Weisbecker, Vera
Salisbury, Steven W.
author_facet Ristevski, Jorgo
Yates, Adam M.
Price, Gilbert J.
Molnar, Ralph E.
Weisbecker, Vera
Salisbury, Steven W.
author_sort Ristevski, Jorgo
collection PubMed
description The crocodylian fossil record from the Cenozoic of Australasia is notable for its rich taxonomic diversity, and is primarily represented by members of the clade Mekosuchinae. Reports of crocodylian fossils from Australia date back to the late nineteenth century. In 1886, Charles Walter de Vis proposed the name Pallimnarchus pollens for crocodylian fossils from southeast Queensland—the first binomen given to an extinct crocodylian taxon from Australia. Pallimnarchus has come to be regarded as a large, broad-snouted crocodylian from Australia’s Plio-Pleistocene, and numerous specimens, few of which are sufficiently complete, have been assigned to it by several authors throughout the twentieth century. In the late 1990s, the genus was expanded to include a second species, Pallimnarchus gracilis. Unfortunately, the original syntype series described as Pallimnarchus pollens is very fragmentary and derives from more than one taxon, while a large part of the subsequently selected lectotype specimen is missing. Because descriptions and illustrations of the complete lectotype do not reveal any autapomorphic features, we propose that Pallimnarchus pollens should be regarded as a nomen dubium. Following this decision, the fossil material previously referred to Pallimnarchus is of uncertain taxonomic placement. A partial skull, formerly assigned to Pallimnarchus pollens and known as ‘Geoff Vincent’s specimen’, possesses many features of diagnostic value and is therefore used as basis to erect a new genus and species—Paludirex vincenti gen. et sp. nov. A comprehensive description is given for the osteology of ‘Geoff Vincent’s specimen’ as well as aspects of its palaeoneurology, the latter being a first for an extinct Australian crocodyliform. The newly named genus is characterized by a unique combination of premaxillary features such as a distinctive arching of the anterior alveolar processes of the premaxillae, a peculiar arrangement of the first two premaxillary alveoli and a large size disparity between the 3rd and 4th premaxillary alveoli. These features presently allow formal recognition of two species within the genus, Paludirex vincenti and Paludirex gracilis comb. nov., with the former having comparatively more robust rostral proportions than the latter. The Paludirex vincenti holotype comes from the Pliocene Chinchilla Sand of the Darling Downs, south-eastern Queensland, whereas the material assigned to Paludirex gracilis is from the Pleistocene of Terrace Site Local Fauna, Riversleigh, northwest Queensland. Phylogenetic analyses recover Paludirex vincenti as a mekosuchine, although further cladistic assessments are needed to better understand the relationships within the clade.
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spelling pubmed-77591362020-12-31 Australia’s prehistoric ‘swamp king’: revision of the Plio-Pleistocene crocodylian genus Pallimnarchus de Vis, 1886 Ristevski, Jorgo Yates, Adam M. Price, Gilbert J. Molnar, Ralph E. Weisbecker, Vera Salisbury, Steven W. PeerJ Paleontology The crocodylian fossil record from the Cenozoic of Australasia is notable for its rich taxonomic diversity, and is primarily represented by members of the clade Mekosuchinae. Reports of crocodylian fossils from Australia date back to the late nineteenth century. In 1886, Charles Walter de Vis proposed the name Pallimnarchus pollens for crocodylian fossils from southeast Queensland—the first binomen given to an extinct crocodylian taxon from Australia. Pallimnarchus has come to be regarded as a large, broad-snouted crocodylian from Australia’s Plio-Pleistocene, and numerous specimens, few of which are sufficiently complete, have been assigned to it by several authors throughout the twentieth century. In the late 1990s, the genus was expanded to include a second species, Pallimnarchus gracilis. Unfortunately, the original syntype series described as Pallimnarchus pollens is very fragmentary and derives from more than one taxon, while a large part of the subsequently selected lectotype specimen is missing. Because descriptions and illustrations of the complete lectotype do not reveal any autapomorphic features, we propose that Pallimnarchus pollens should be regarded as a nomen dubium. Following this decision, the fossil material previously referred to Pallimnarchus is of uncertain taxonomic placement. A partial skull, formerly assigned to Pallimnarchus pollens and known as ‘Geoff Vincent’s specimen’, possesses many features of diagnostic value and is therefore used as basis to erect a new genus and species—Paludirex vincenti gen. et sp. nov. A comprehensive description is given for the osteology of ‘Geoff Vincent’s specimen’ as well as aspects of its palaeoneurology, the latter being a first for an extinct Australian crocodyliform. The newly named genus is characterized by a unique combination of premaxillary features such as a distinctive arching of the anterior alveolar processes of the premaxillae, a peculiar arrangement of the first two premaxillary alveoli and a large size disparity between the 3rd and 4th premaxillary alveoli. These features presently allow formal recognition of two species within the genus, Paludirex vincenti and Paludirex gracilis comb. nov., with the former having comparatively more robust rostral proportions than the latter. The Paludirex vincenti holotype comes from the Pliocene Chinchilla Sand of the Darling Downs, south-eastern Queensland, whereas the material assigned to Paludirex gracilis is from the Pleistocene of Terrace Site Local Fauna, Riversleigh, northwest Queensland. Phylogenetic analyses recover Paludirex vincenti as a mekosuchine, although further cladistic assessments are needed to better understand the relationships within the clade. PeerJ Inc. 2020-12-21 /pmc/articles/PMC7759136/ /pubmed/33391869 http://dx.doi.org/10.7717/peerj.10466 Text en © 2020 Ristevski et al. https://creativecommons.org/licenses/by/4.0/ This is an open access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/) , which permits unrestricted use, distribution, reproduction and adaptation in any medium and for any purpose provided that it is properly attributed. For attribution, the original author(s), title, publication source (PeerJ) and either DOI or URL of the article must be cited.
spellingShingle Paleontology
Ristevski, Jorgo
Yates, Adam M.
Price, Gilbert J.
Molnar, Ralph E.
Weisbecker, Vera
Salisbury, Steven W.
Australia’s prehistoric ‘swamp king’: revision of the Plio-Pleistocene crocodylian genus Pallimnarchus de Vis, 1886
title Australia’s prehistoric ‘swamp king’: revision of the Plio-Pleistocene crocodylian genus Pallimnarchus de Vis, 1886
title_full Australia’s prehistoric ‘swamp king’: revision of the Plio-Pleistocene crocodylian genus Pallimnarchus de Vis, 1886
title_fullStr Australia’s prehistoric ‘swamp king’: revision of the Plio-Pleistocene crocodylian genus Pallimnarchus de Vis, 1886
title_full_unstemmed Australia’s prehistoric ‘swamp king’: revision of the Plio-Pleistocene crocodylian genus Pallimnarchus de Vis, 1886
title_short Australia’s prehistoric ‘swamp king’: revision of the Plio-Pleistocene crocodylian genus Pallimnarchus de Vis, 1886
title_sort australia’s prehistoric ‘swamp king’: revision of the plio-pleistocene crocodylian genus pallimnarchus de vis, 1886
topic Paleontology
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7759136/
https://www.ncbi.nlm.nih.gov/pubmed/33391869
http://dx.doi.org/10.7717/peerj.10466
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