Large dissorophoid skeletal elements from the Lower Permian Richards Spur Fissures, Oklahoma, and their paleoecological implications

Abstract

ABSTRACT Skeletal remains attributable to large dissorophoid amphibians, including four femora, two humeri, and an isolated palatine bone, have recently been recovered from the Lower Permian fissure fill deposits at Richards Spur, Oklahoma. Three of the femora are assignable to Acheloma cumminsi. One humérus represents an indeterminate trematopid, perhaps A. cumminsi, whereas the remaining humerus and femur are evidently of dissorophid origin and probably assignable to Cacops. The palatine bone is of unusual morphology and evidently represents a third distinct large dissorophoid taxon. Although the Richards Spur faunal assemblage is unquestionably dominated by small animals such as Captorhinus aguti, Cardiocephalus, and Euryodus, the discovery of rare, larger skeletal elements at the site implies that some elements of the fauna approached or slightly exceeded a body length of about one meter. Although probably uncommon in the vicinity of the fissures, such larger species were clearly not excluded from the deposits by preservational biases. Like other taxa known from Richards Spur, the dissorophoids were fully terrestrial as adults, and their presence reinforces previous interpretations of the Richards Spur paleoenvironment as an arid highland region. However, some Richards Spur taxa have also been reported from lowland “deltaic” localities such as South Grandfield, Oklahoma, implying that their distribution was more cosmopolitan.