''Xenocretosuchus'' is an extinct genus of

tritylodont Tritylodontidae ("three-knob teeth", named after the shape of their cheek teeth) is an extinct family of small to medium-sized, highly specialized mammal-like cynodonts, bearing several mammalian traits like erect limbs, endothermy and details ...

therapsids Therapsida is a major group of eupelycosaurian synapsids that includes mammals, their ancestors and relatives. Many of the traits today seen as unique to mammals had their origin within early therapsids, including limbs that were oriented mor ...

from the

Aptian The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous Epoch or Series and encompasses the time from 121.4 ± 1.0 Ma to 113.0 ± 1.0 Ma (million years ago), a ...

(

Early Cretaceous The Early Cretaceous ( geochronological name) or the Lower Cretaceous (chronostratigraphic name), is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 145 Ma to 100.5 Ma. Geology Pro ...

)

Ilek Formation The Ilek Formation is a Lower Cretaceous geologic formation in Western Siberia. Many different fossils have been recovered from the formation. It overlies the Late Jurassic Tyazhin Formation and underlies the Albian Kiya Formation. The formation ...

Siberia Siberia ( ; rus, Сибирь, r=Sibir', p=sʲɪˈbʲirʲ, a=Ru-Сибирь.ogg) is an extensive geographical region, constituting all of North Asia, from the Ural Mountains in the west to the Pacific Ocean in the east. It has been a part of ...

, in the

Russian Federation Russia (, , ), or the Russian Federation, is a List of transcontinental countries, transcontinental country spanning Eastern Europe and North Asia, Northern Asia. It is the List of countries and dependencies by area, largest country in the ...

.Fossilworks. "Xenocretosuchus." Retrieved from
/ref> The type species, ''X. sibiricus'', is known only from dental elements,
/ref> as is ''X. kolossovi'', described from the

Batylykh Formation The Batylykh Formation is a geological formation in Yakutia, Russia. It is of an uncertain Early Cretaceous age, probably dating between the Berriasian and the Barremian. It is the oldest unit of the thick Sangar Series within the Vilyuy syne ...

in 2008.Lopatin & Agadjanian, 2008. "A Tritylodont (Tritylodontidae, Synapsida) from the Mesozoic of Yakutia." Retrieved fro

/ref> Some authors have treated these species as part of the genus ''

Stereognathus ''Stereognathus'' is an extinct genus of tritylodontid cynodonts from the Middle Jurassic of the United Kingdom. There is a single named species: ''S. ooliticus'', named after the Great Oolite deposits of England. A second species, ''S. hebridic ...

,'' otherwise known from the Middle Jurassic of Britain But this is rejected by other authors. Alongside ''

Montirictus ''Montirictus'' is an extinct genus of Tritylodontidae, tritylodonts known from the Early Cretaceous Kuwajima Formation of Japan. It is currently the latest surviving tritylodontid species, and is closely related to the earlier ''Xenocretosuchus ...

'' and '' Fossiomanus'', it is amongst the latest known non-

mammaliform Mammaliaformes ("mammalian forms") is a clade that contains the crown group mammals and their closest extinct relatives; the group radiated from earlier probainognathian cynodonts. It is defined as the clade originating from the most recen ...

synapsid Synapsids + (, 'arch') > () "having a fused arch"; synonymous with ''theropsids'' (Greek, "beast-face") are one of the two major groups of animals that evolved from basal amniotes, the other being the sauropsids, the group that includes reptil ...

, extending their range to the Early Cretaceous.

References

Early Cretaceous synapsids Prehistoric cynodont genera Extinct animals of Russia Tritylodontids Fossil taxa described in 1999 {{paleo-therapsid-stub