An Early Permian varanodontine varanopid (Synapsida: Eupelycosauria) from the Richards Spur locality, Oklahoma (original) (raw)

Description of the first varanodontine varanopid material from the highly fossiliferous limestone fissure fill deposits at Richards Spur (Dolese Brothers Limestone Quarry), Oklahoma, is based on elements of at least three individuals recovered from two separate blocks of sedimentary rock. One block, which yielded associated cranial and postcranial bones from both adult and juvenile individuals, includes two well-preserved parabasisphenoid complexes, vertebrae, forelimb, pelvic girdle, and hind limb bones. An isolated maxilla fragment from another block preserves the diagnostic dorsal process characteristic of varanodontines. Preserved cranial and postcranial material is virtually identical to the varanodontine Varanops brevirostris. Taxonomic assessment of this new material in the context of the most comprehensive phylogenetic analysis of Varanopidae to date indicates the Richards Spur varanodontine is referable to Varanops brevirostris based on distinctive characters of the maxilla and the parabasisphenoid. The large size of Varanops suggests it was one of the top predators of the Richards Spur ecosystem. The Richards Spur locality records the only known co-occurrence of a mycterosaurine and a varanodontine varanopid at a single locality, and varanopids are the most common synapsids in the assemblage. As generally rare components of the more typically preserved lowland environments, the relative abundance and diversity of varanopids at Richards Spur suggests that they may have been more common components of the upland ecosystems in the Early Permian.