''Eorhynchochelys'' (meaning "dawn-beaked turtle" in

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

) is an extinct

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

of stem-

turtle Turtles are an order of reptiles known as Testudines, characterized by a special shell developed mainly from their ribs. Modern turtles are divided into two major groups, the Pleurodira (side necked turtles) and Cryptodira (hidden necked tu ...

from the Late Triassic

Xiaowa Formation The Xiaowa Formation is a Carnian-age geological formation found in southern China. It is a sequence of limestone and marls from the Carnian stage of the Triassic. Its lower section was previously known as the Wayao Formation or Wayao Member of th ...

(or Wayao Member of the Falang Formation) of southwestern China.

Description

''Eorhynchochelys'' is notable for its unusual combination of a turtle-style skull and a conventional reptilian body. The skull, for example, has an edentulous beak typical of all members of Testudinata. However, the thorax region is markedly different from ''

Pappochelys ''Pappochelys'' (''παπποχέλυς'' �άππος (grandfather) + χέλυς (turtle)meaning "grandfather turtle" in Ancient Greek, Greek) is an extinct genus of diapsid reptile possibly related to turtles. The genus contains only one spe ...

'' and ''

Odontochelys ''Odontochelys semitestacea'' (meaning "toothed turtle with a half-shell") is a Late Triassic relative of turtles. Before ''Pappochelys'' was discovered and '' Eunotosaurus'' was redescribed, ''Odontochelys'' was considered the oldest undisputed ...

'' and more similar to ''

Eunotosaurus ''Eunotosaurus'' (''Latin'': Stout-backed lizard) is an extinct genus of amniote, possibly a close relative of turtles. ''Eunotosaurus'' lived in the late Middle Permian (Capitanian stage) and fossils can be found in the Karoo Supergroup of Sout ...

'' in lacking a shell, even though the ribs were wide and flat. The skull also has a single pair of holes behind the skull, unlike the presence of two pairs of holes in ''Pappochelys''. Unlike other stem-turtles, ''Eorhynchochelys'' had twelve dorsal vertebrae. It reached up to in total length, which is much larger than ''Pappochelys''.

References

Pantestudines Triassic reptiles of Asia Transitional fossils Fossil taxa described in 2018 Prehistoric reptile genera {{Paleo-turtle-stub