''Yakemys'' is an extinct genus of macrobaenid turtles from the Late Jurassic-Early Cretaceous (

Tithonian In the geological timescale, the Tithonian is the latest age (geology), age of the Late Jurassic Epoch and the uppermost stage (stratigraphy), stage of the Upper Jurassic Series. It spans the time between 149.2 ±0.7 annum, Ma and 143.1 ±0.6 (mi ...

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 ...

?) lower

Phu Kradung Formation The Early Cretaceous Phu Kradung Formation is the lowest member of the Mesozoic Khorat Group which outcrops on the Khorat Plateau in Isan, Thailand. This geological formation consists of micaceous, brown to reddish-brown siltstone beds with mino ...

Thailand Thailand, officially the Kingdom of Thailand and historically known as Siam (the official name until 1939), is a country in Southeast Asia on the Mainland Southeast Asia, Indochinese Peninsula. With a population of almost 66 million, it spa ...

. It is monotypic, containing a single species, ''Yakemys multiporcata''.

Discovery and etymology

''Yakemys'' hails from fossil turtle site Ban Huai Yang (บ้านห้วยยาง) of Northeast Thailand, which, although expected to be within the later Phra Wihan Formation based on its geographic location, is thought to instead belong to the

based on sedimentology. The recovered holotype of ''Yakemys multiporcata'' SM KS39 (housed in the

Sirindhorn Museum Sirindhorn Museum (aka Sirindhorn Dinosaur Museum) () is a geology museum in northeast Thailand. It is located at Non Buri, Sahatsakhan district, Kalasin province. About Dinosaur fossils were found by Phra Kru Vijitsahassakun, the abbot of Wa ...

) consists of a very partial shell, and the paratypes PRC 151, PRC 152, and PRC 153, each one or two shell fragments from different individuals. Its genus name is derived from ยักษ์ (''yak''), meaning "giant" in Thai, and its specific name from Latin "multus" (multiple) and "porca" (ridge).

Description

''Yakemys'' is one of the earliest macrobaenids known, and one of the three largest, with a carapace length of 70 cm (2.3 ft), equaling '' Anatolemys maximus'' and '' Judithemys backmani'' from the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the more recent of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''cre ...

and

Paleocene The Paleocene ( ), or Palaeocene, is a geological epoch (geology), epoch that lasted from about 66 to 56 mya (unit), million years ago (mya). It is the first epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), ...

. It can be distinguished by these

autapomorphies In phylogenetics, an autapomorphy is a distinctive feature, known as a derived trait, that is unique to a given taxon. That is, it is found only in one taxon, but not found in any others or outgroup taxa, not even those most closely related to ...

: narrow vertebral scutes, large lateral longitudinal keels on the vertebral region, a plastron greatly reduced in size compared to the carapace, among other traits.

Classification

''Yakemys'' was found by phylogenetic analysis in Tong ''et al.'' (2021) to belong to

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 ...

, and they suggested that

Sinemydidae Sinemydidae is an extinct family of turtles from the Jurassic and Cretaceous of East Asia. Their exact position is engimatic, they have alternatively been considered stem-group cryptodires, but also "crownward stem-turtles" alongside Macrobaen ...

is a subfamily of

, becoming Sinemydinae. The results of the analysis are shown below:

References

{{Taxonbar, from=Q110127889 Macrobaenidae Prehistoric turtle genera Fossil taxa described in 2021