These sediments have produced many skeletal remains of diverse amniotes, but most importantly, a partial skull of “a small synapsid of varanopseid affinities”, Mesenosaurus romeri.

Its nearly complete skull and mandible was discovered at Richards Spur locality within a series of infilled karst fissures in the Ordovician Arbuckle limestone in Oklahoma, which is one of the most plentiful sites for early Permian tetrapod fossils.

[4] In terms of classifying M. efremovi, it shares distinct cranial features with mycterosaurines (stem based group that includes Mycterosaurus longiceps and all varanopseids related more closely to it than to Varanodon agilis), such as the “exclusion of the lacrimal from the external naris and an anteroposteriorly broad dorsal lamina of the maxilla that underlies the nasal and contacts the prefrontal”.

Some of these shared features include relative size and shape of the temporal fenestra, lateral swelling of the maxilla in the caniniform region and five premaxillary tooth positions (not reported in other mycterosaurines).

Further research on postcranial features is required in order to determine if this hypothesis is correct, as we would need to observe a similar degree of stasis throughout the entire skeleton.

Mesenosaurus represents a guild of highly agile subordinate predators[1][9] in their communities due to their large, slender, curved teeth, which could cause severe wounds when piercing its prey.

[10] Many varanopids were arboreal, however the well-developed olecranon(bony prominence of the elbow) of Mesenosaurus indicates the presence of triceps and anconeus muscle,[12][13][14] both of which would provide powerful forearm extension.

This is based on the presence of a rearward shift of center of body mass (slender trunks, elongated hindlimbs, and short forelimbs) that is necessary for facultative bipedalism.