Publication Date:
2015-06-25
Description:
The origin and early evolution of turtles have long been major contentious issues in vertebrate zoology. This is due to conflicting character evidence from molecules and morphology and a lack of transitional fossils from the critical time interval. The approximately 220-million-year-old stem-turtle Odontochelys from China has a partly formed shell and many turtle-like features in its postcranial skeleton. Unlike the 214-million-year-old Proganochelys from Germany and Thailand, it retains marginal teeth and lacks a carapace. Odontochelys is separated by a large temporal gap from the approximately 260-million-year-old Eunotosaurus from South Africa, which has been hypothesized as the earliest stem-turtle. Here we report a new reptile, Pappochelys, that is structurally and chronologically intermediate between Eunotosaurus and Odontochelys and dates from the Middle Triassic period ( approximately 240 million years ago). The three taxa share anteroposteriorly broad trunk ribs that are T-shaped in cross-section and bear sculpturing, elongate dorsal vertebrae, and modified limb girdles. Pappochelys closely resembles Odontochelys in various features of the limb girdles. Unlike Odontochelys, it has a cuirass of robust paired gastralia in place of a plastron. Pappochelys provides new evidence that the plastron partly formed through serial fusion of gastralia. Its skull has small upper and ventrally open lower temporal fenestrae, supporting the hypothesis of diapsid affinities of turtles.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Schoch, Rainer R -- Sues, Hans-Dieter -- England -- Nature. 2015 Jul 30;523(7562):584-7. doi: 10.1038/nature14472. Epub 2015 Jun 24.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Staatliches Museum fur Naturkunde Stuttgart, Rosenstein 1, D-70191 Stuttgart, Germany. ; Department of Paleobiology, National Museum of Natural History, MRC 121, PO Box 37012, Washington, District of Columbia 20013-7012, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26106865" target="_blank"〉PubMed〈/a〉
Keywords:
Animal Shells
;
Animals
;
*Biological Evolution
;
*Fossils
;
Germany
;
Phylogeny
;
Skull/anatomy & histology
;
Turtles/*anatomy & histology/classification
Print ISSN:
0028-0836
Electronic ISSN:
1476-4687
Topics:
Biology
,
Chemistry and Pharmacology
,
Medicine
,
Natural Sciences in General
,
Physics
