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| Eorhynchochelys sinensis |
Abstract
The early evolution of turtles continues to be a contentious issue in vertebrate palaeontology. Recent reports have suggested that they are diapsids but the position of turtles within Diapsida is controversial and the sequence of acquisition of turtle synapomorphies remains unclear. Here we describe a Triassic turtle from China that has a mixture of derived characters and plesiomorphic features. To our knowledge, it represents the earliest known stem turtle with an edentulous beak and a rigid puboischiadic plate. The discovery of this new form reveals a complex early history of turtles.
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| Fig. 1: The holotype of Eorhynchochelys sinensis (SMMP 000016). Complete articulated skeleton, as preserved. |
Reptilia Laurenti, 1768
Pantestudines Joyce, Parham and Gauthier, 200414
Eorhynchochelys sinensis gen. et sp. nov.
Etymology. Eo- (dawn), rhyncho- (beak), chelys (turtle): the earliest turtle with a beak; sinensis, from China. ("Ay-oh-rink-oh-keel-is")
Holotype. Sanya Museum of Marine Paleontology (SMMP) 000016 in Hainan Province, China, an articulated specimen displaying the postcranium in dorsal view, and the skull in ventral view (the skull and pelvis were prepared from both sides).
Locality. Heshangjing of Baiyuncun, Xinpuxiang, Guanling District, Guizhou Province, southwestern China.
Horizon. The upper unit of the lower part of the Wayao Member of the Falang Formation, approximately 8.5 m above the top of the Zhuganpo Member; Late Triassic (Carnian age).
Diagnosis. A stem pantestudine of large size; proportionately small skull broadly triangular in outline; supratemporal fenestra closed; infratemporal fenestra partially open; edentulous beak; pleurodont tooth implantation; teeth on parabasisphenoid; 12 dorsal vertebrae; neural spines with disc-like dorsal tables in cervical vertebra 8 to caudal 5; dorsal ribs 1 through 10 horizontally (anteroposteriorly) broadened, T-shaped in cross-section; rigid puboischiadic plate with median ventral keel; and ischium with posterior elongation.
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Chun Li, Nicholas C. Fraser, Olivier Rieppel and Xiao-Chun Wu. 2018. A Triassic Stem Turtle with An Edentulous Beak. Nature. 560; 476–479. DOI: 10.1038/s41586-018-0419-1
230-million-year-old turtle fossil deepens mystery of reptile's origins nature.com/articles/d41586-018-06012-0
Fossil turtle didn't have a shell yet, but had the first toothless turtle beak phys.org/news/2018-08-fossil-turtle-didnt-shell-toothless.html via @physorg_com
