| Ordosiodon Temporal range:Early Triassic | |
|---|---|
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Synapsida |
| Clade: | Therapsida |
| Clade: | †Therocephalia |
| Superfamily: | †Baurioidea |
| Genus: | †Ordosiodon Young, 1961 |
| Species | |
Ordosiodon is an extinctgenus oftherocephaliantherapsids from theEarly Triassic of China. It includes two species,O. lincheyuensis andO. youngi.
O. lincheyuensis, thetype species, was named by Chinese paleontologistC. C. Young (Yang Zhongjian) in 1961 on the basis of a partial lower jaw.[1] The jaw was discovered by a petroleum survey team in October 1958 from the LowerErmaying Formation inShanxi Province,[2] which dates back to theOlenekian stage.[3] Young named the genus after theOrdos Desert, the region where the jaw was found.[4]Ordosiodon was originally identified as a type ofdiademodontid by Young (diademodontids are herbivorouscynodonts that are much more closely related to mammals than are therocephalians). Young noted several unusual features ofOrdosiodon that set it apart from diademodontids, including the lack of adiastema or gap in the teeth, the lack of molar-likesectorial teeth at the back of the jaw, conicalcaniniform teeth, and relatively small postcaniniform teeth.Ordosiodon was later identified as a juvenile diademodontid to account for these differences.[5]
In 1979 a partial skull and skeleton was found from the same area asO. lincheyuensis and namedOrdosia youngi in honor of Young.[6]O. youngi was identified as a therocephalian and placed in the family Ordosiidae. Distinguishing characteristics ofO. youngi include an elongatedsecondary palate on the underside of the skull, a short snout, and a temporal (cheek) region that is wider than the back of the skull. The postcaniniform teeth increase in size farther back in the jaws.[5]
In 1981 the jaw ofOrdosiodon was recognized as that of a therocephalian similar toOrdosia youngi.Ordosia became asynonym ofOrdosiodon andOrdosia youngi was reclassified asOrdosiodon youngi. The namesOrdosia andOrdosiidae are now occupied by a genus and family ofCambriantrilobites.[5]
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