Pappochelys

Pappochelys Temporal range: Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
The holotype specimen of Pappochelys
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Clade:	Pantestudines
Genus:	†Pappochelys Schoch & Sues 2015
Type species
†Pappochelys rosinae Schoch & Sues 2015

Pappochelys (παπποχέλυς [πάππος (grandfather) + χέλυς (turtle)] meaning "grandfather turtle" in

Pappochelys had a wide body, small skull, and a long tail that makes up about half of the total body length, which is up to 20 centimetres (8 in). The skull is pointed with large eye sockets. Several turtle-like features are present, including expanded ribs and

Fossils of Pappochelys come from a rock group in Germany called the

Of the reptiles that most closely resemble Pappochelys, Eunotosaurus was originally classified as a parareptile and Odontochelys has always been classified as a stem-turtle (stem-turtles are taxa more closely related to turtles than they are to any other living reptile group, but are not themselves turtles).

In their description of Chinlechelys, Lichtig & Lucas (2021) criticized Schoch & Sue's hypothesis of turtle origins, particularly the idea shells evolved from broadening ribs with no osteoderms involved (as Pappochelys apparently indicates). Instead, they proposed Pappochelys was actually a sauropterygian related to placodonts while turtles were derived parareptiles.^[8]

Paleobiology

The claystone bed in which fossils of Pappochelys were found was likely deposited in a lake setting,^[3] suggesting that Pappochelys may have been semi-aquatic like modern turtles. Although Pappochelys lacked a fully formed shell like modern turtles, its thickened bones may have helped reduce the body's buoyancy, making it a more adept swimmer.^[1] However, otherwise the anatomy has no signs of a fully aquatic lifestyle^[3] and only few adaptations for swimming. In addition, a histological study found that its limb bones had a thick outer wall and small, open (rather than spongy) medullary cavity, like only a few aquatic reptiles and completely unlike modern aquatic turtles. These features have also been recorded in terrestrial reptiles such as the modern lizard Sceloporus and Eunotosaurus, another genus of pantestudine with burrowing adaptations. This may indicate that Pappochelys had a burrowing or modestly aquatic lifestyle, rather than a fully aquatic one.^[9]

References