Terrestrial origin of viviparity in mesozoic marine reptiles indicated by early triassic embryonic fossils.

Viviparity in Mesozoic marine reptiles has traditionally been considered an aquatic adaptation. We report a new fossil specimen that strongly contradicts this traditional interpretation. The new specimen contains the oldest fossil embryos of Mesozoic marine reptile that are about 10 million years ol...

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Autores principales:	Ryosuke Motani, Da-yong Jiang, Andrea Tintori, Olivier Rieppel, Guan-bao Chen
Formato:	article
Lenguaje:	EN
Publicado:	Public Library of Science (PLoS) 2014
Materias:	Medicine R Science Q
Acceso en línea:	https://doaj.org/article/e4ffe35189c74d7882d36c3c8a3320ee
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spelling	oai:doaj.org-article:e4ffe35189c74d7882d36c3c8a3320ee2021-11-18T08:32:46ZTerrestrial origin of viviparity in mesozoic marine reptiles indicated by early triassic embryonic fossils.1932-620310.1371/journal.pone.0088640https://doaj.org/article/e4ffe35189c74d7882d36c3c8a3320ee2014-01-01T00:00:00Zhttps://www.ncbi.nlm.nih.gov/pmc/articles/pmid/24533127/pdf/?tool=EBIhttps://doaj.org/toc/1932-6203Viviparity in Mesozoic marine reptiles has traditionally been considered an aquatic adaptation. We report a new fossil specimen that strongly contradicts this traditional interpretation. The new specimen contains the oldest fossil embryos of Mesozoic marine reptile that are about 10 million years older than previous such records. The fossil belongs to Chaohusaurus (Reptilia, Ichthyopterygia), which is the oldest of Mesozoic marine reptiles (ca. 248 million years ago, Early Triassic). This exceptional specimen captures an articulated embryo in birth position, with its skull just emerged from the maternal pelvis. Its headfirst birth posture, which is unlikely to be a breech condition, strongly indicates a terrestrial origin of viviparity, in contrast to the traditional view. The tail-first birth posture in derived ichthyopterygians, convergent with the conditions in whales and sea cows, therefore is a secondary feature. The unequivocally marine origin of viviparity is so far not known among amniotes, a subset of vertebrate animals comprising mammals and reptiles, including birds. Therefore, obligate marine amniotes appear to have evolved almost exclusively from viviparous land ancestors. Viviparous land reptiles most likely appeared much earlier than currently thought, at least as early as the recovery phase from the end-Permian mass extinction.Ryosuke MotaniDa-yong JiangAndrea TintoriOlivier RieppelGuan-bao ChenPublic Library of Science (PLoS)articleMedicineRScienceQENPLoS ONE, Vol 9, Iss 2, p e88640 (2014)
institution	DOAJ
collection	DOAJ
language	EN
topic	Medicine R Science Q
spellingShingle	Medicine R Science Q Ryosuke Motani Da-yong Jiang Andrea Tintori Olivier Rieppel Guan-bao Chen Terrestrial origin of viviparity in mesozoic marine reptiles indicated by early triassic embryonic fossils.
description	Viviparity in Mesozoic marine reptiles has traditionally been considered an aquatic adaptation. We report a new fossil specimen that strongly contradicts this traditional interpretation. The new specimen contains the oldest fossil embryos of Mesozoic marine reptile that are about 10 million years older than previous such records. The fossil belongs to Chaohusaurus (Reptilia, Ichthyopterygia), which is the oldest of Mesozoic marine reptiles (ca. 248 million years ago, Early Triassic). This exceptional specimen captures an articulated embryo in birth position, with its skull just emerged from the maternal pelvis. Its headfirst birth posture, which is unlikely to be a breech condition, strongly indicates a terrestrial origin of viviparity, in contrast to the traditional view. The tail-first birth posture in derived ichthyopterygians, convergent with the conditions in whales and sea cows, therefore is a secondary feature. The unequivocally marine origin of viviparity is so far not known among amniotes, a subset of vertebrate animals comprising mammals and reptiles, including birds. Therefore, obligate marine amniotes appear to have evolved almost exclusively from viviparous land ancestors. Viviparous land reptiles most likely appeared much earlier than currently thought, at least as early as the recovery phase from the end-Permian mass extinction.
format	article
author	Ryosuke Motani Da-yong Jiang Andrea Tintori Olivier Rieppel Guan-bao Chen
author_facet	Ryosuke Motani Da-yong Jiang Andrea Tintori Olivier Rieppel Guan-bao Chen
author_sort	Ryosuke Motani
title	Terrestrial origin of viviparity in mesozoic marine reptiles indicated by early triassic embryonic fossils.
title_short	Terrestrial origin of viviparity in mesozoic marine reptiles indicated by early triassic embryonic fossils.
title_full	Terrestrial origin of viviparity in mesozoic marine reptiles indicated by early triassic embryonic fossils.
title_fullStr	Terrestrial origin of viviparity in mesozoic marine reptiles indicated by early triassic embryonic fossils.
title_full_unstemmed	Terrestrial origin of viviparity in mesozoic marine reptiles indicated by early triassic embryonic fossils.
title_sort	terrestrial origin of viviparity in mesozoic marine reptiles indicated by early triassic embryonic fossils.
publisher	Public Library of Science (PLoS)
publishDate	2014
url	https://doaj.org/article/e4ffe35189c74d7882d36c3c8a3320ee
work_keys_str_mv	AT ryosukemotani terrestrialoriginofviviparityinmesozoicmarinereptilesindicatedbyearlytriassicembryonicfossils AT dayongjiang terrestrialoriginofviviparityinmesozoicmarinereptilesindicatedbyearlytriassicembryonicfossils AT andreatintori terrestrialoriginofviviparityinmesozoicmarinereptilesindicatedbyearlytriassicembryonicfossils AT olivierrieppel terrestrialoriginofviviparityinmesozoicmarinereptilesindicatedbyearlytriassicembryonicfossils AT guanbaochen terrestrialoriginofviviparityinmesozoicmarinereptilesindicatedbyearlytriassicembryonicfossils
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Terrestrial origin of viviparity in mesozoic marine reptiles indicated by early triassic embryonic fossils.

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