Sinemydidae is an extinct family of

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

s from the Jurassic and Cretaceous of East Asia. Their exact position is engimatic, they have alternatively been considered stem-group

cryptodires The Cryptodira (') are a suborder of Testudines that includes most living tortoises and turtles. Cryptodira is commonly called the "Hidden-Neck Turtles" or the "Inside-Neck Turtles". Cryptodira differ from Pleurodira (side-necked turtles) in th ...

, but also "crownward stem-turtles" alongside

Macrobaenidae Macrobaenidae is an extinct family of turtles, known from the Early Cretaceous to Paleogene of Laurasia. Their relationships to other turtles and whether they form a monophlyletic group are controversial. They are typically interpreted as stem o ...

Paracryptodira __NOTOC__ Paracryptodira is an extinct group of reptiles in the clade Testudinata (which contains modern turtles and their extinct relatives), known from the Jurassic to Paleogene of North America and Europe. Initially treated as a suborder siste ...

Xinjiangchelyidae Xinjiangchelyidae is an extinct family of turtles known from the Lower Jurassic to the Middle Cretaceous of Asia and western Europe. They have generally been interpreted as either being basal Cryptodira, cryptodires or placed outside of crown Tes ...

Thalassochelydia Thalassochelydia is a clade of extinct marine turtles from the Late Jurassic and earliest Cretaceous of Europe and South America. The group is defined as including '' Eurysternum'', ''Plesiochelys'' and '' Thalassemys'' to the exclusion of '' Pel ...

and

Sandownidae Sandownidae is a family of extinct marine turtles from the Cretaceous and Paleogene distributed around the Atlantic Ocean and adjacent areas. The family is defined as all taxa closer to the type genus '' Sandownia'' than to '' Pelomedusa'', '' Te ...

outside of crown Testudines.

Genera

*'' Dracochelys'' Lianmugin Formation, China, Early Cretaceous (Aptian-Albian) *'' Hongkongochelys'' Upper

Shaximiao Formation The Shaximiao Formation () is a Middle to Late Jurassic aged geological formation in Sichuan, China, most notable for the wealth of dinosaurs fossils that have been excavated from its strata. The Shaximiao Formation is exposed in and around the ...

, China, Middle-Late Jurassic *''

Jeholochelys ''Jeholochelys'' is an extinct genus of sinemydid turtle that lived during the Early Cretaceous of what is now China. The holotype specimen was discovered in the Jiufotang Formation of Sihedang in Lingyuan, western Liaoning. In 2018, the Chines ...

Jiufotang Formation The Jiufotang Formation () is an Early Cretaceous geological formation in Chaoyang, Liaoning which has yielded fossils of feathered dinosaurs, primitive birds, pterosaurs, and other organisms (see Jehol Biota). It is a member of the Jehol group. T ...

, China, Early Cretaceous (Aptian) *'' Liaochelys'' Jiufotang Formation, China, Early Cretaceous (Aptian) *''

Manchurochelys ''Manchurochelys'' is an extinct genus of turtle. It existed during the early Cretaceous of what is now northeast China. It has been found in the Jianshangou Bed of West Liaoning's Yixian Formation. However, it is a rarely found fossil. ''Manchu ...

Yixian Formation The Yixian Formation (; formerly Romanization of Chinese, transcribed as Yihsien Formation or Yixiang Formation) is a geological formation in Jinzhou, Liaoning, People's Republic of China, that spans the Barremian stage of the Early Cretaceous. I ...

, China, Early Cretaceous (Aptian) *''

Ordosemys ''Ordosemys'' is an extinct genus of turtle from the Cretaceous period The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the ...

'' **''O''. ''leios'' Luohandong Formation, China, Early Cretaceous **''O''. ''liaoxiensis'' Chengzihe Formation, China, Early Cretaceous (Aptian) **''O''. ''brinkmania'' Lianmugin Formation, China, Early Cretaceous (Aptian-Albian) **''O''. ''perforata'' Khulsangol Formation, Mongolia, Early Cretaceous (Albian) **''O''. ''donghai'' Chengzihe Formation, China, Early Cretaceous (Aptian-Albian) *''

Sinemys ''Sinemys'' is an extinct genus of turtle from the Late Jurassic to Early Cretaceous of China. Three species have been named: ''S. lens'', the type species, from the Kimmeridgian-Tithonian of Shandong; ''S. gamera'' () (named after the movie mo ...

'' **†''Sinemys brevispinus'' Tong and Brinkman 2012 Laohongdong Formation, China, Early Cretaceous **†''Sinemys chabuensis'' Ji and Chen 2018 Jingchuan Formation, China, Early Cretaceous (

Barremian The Barremian is an age in the geologic timescale (or a chronostratigraphic stage) between 125.77 Ma (million years ago) and 121.4 ± 1.0 Ma (Historically, this stage was placed at 129.4 million to approximately 125 million years ago) It is a ...

) **†''Sinemys gamera'' Brinkman and Peng 1993 Luohandong Formation, China, Early Cretaceous (

Valanginian In the geologic timescale, the Valanginian is an age or stage of the Early or Lower Cretaceous. It spans between 137.05 ± 0.2 Ma and 132.6 ± 0.2 Ma (million years ago). The Valanginian Stage succeeds the Berriasian Stage of the Lower Cretac ...

Hauterivian The Hauterivian is, in the geologic timescale, an age in the Early Cretaceous Epoch or a stage in the Lower Cretaceous Series. It spans the time between 132.6 ± 2 Ma and 125.77 (million years ago). The Hauterivian is preceded by the Valangi ...

) **†''Sinemys lens'' Wiman 1930

Mengyin Formation The Meng-Yin or Mengyin Formation () is a geological formation in Shandong, China, whose strata date back to the Berriasian and Valanginian stages of the Early Cretaceous.Berriasian In the geological timescale, the Berriasian is an age/ stage of the Early/Lower Cretaceous. It is the oldest subdivision in the entire Cretaceous. It has been taken to span the time between 143.1 ±0.6 Ma and 137.05 ± 0.2 (million years ago) ...

-Valanginian) *'' Wuguia'' **†''Wuguia efremovi'' Khozatsky 1996 Hutubei Formation, China, Hauterivian/Barremian Lianmuxin Formation, China, Early Cretaceous (Aptian-Albian) **†''Wuguia hutubeiensis'' Matzke et al. 2004 Hutubei Formation, China, Hauterivian/Barremian *''

Xiaochelys ''Xiaochelys'' is an extinct genus of sinemydid turtle that lived in China during the Early Cretaceous epoch. It is known from a single species A species () is often defined as the largest group of organisms in which any two individuals of ...

'' Lianmugin Formation, China, Early Cretaceous (Aptian-Albian) *'' Yumenemys'' Hui-Hui-P'u, China, Late Cretaceous Material from the Paleocene of California previously attributed to c.f. Sinemyididae is now attributed to macrobaenids.

References

External links

† A dagger, obelisk, or obelus is a typographical mark that usually indicates a footnote if an asterisk has already been used. The symbol is also used to indicate death (of people) or extinction (of species or languages). It is one of the mo ...

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