Cacops

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 humerus 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...

Abstract: Cacops, one of the most distinctive Paleozoic amphibians, is part of a clade of dissorophoid temnospondyls that diversified in the equatorial region of Pangea during the Late Carboniferous and Early Permian, persisting into the Late Permian in Central Russia and China. Dissorophids were a successful group of fully terrestrial, often spectacularly armoured predators, the only amphibians apparently able to coexist with amniotes when the latter started to dominate terrestrial ecosystems. In this paper, we describe excellent new skulls from the Early Permian of Oklahoma attributed to Cacops, Cacops morrisi sp. nov. and provide for the first time detailed information about this iconic dissorophid. These specimens show anatomical and ontogenetic features that will impact on future studies on the evolution of terrestriality in tetrapods. For example, the large, posteriorly closed tympanic embayment has fine striations on an otherwise smooth surface, documenting the oldest known clear evidence for the presence of a tympanic membrane in the fossil record, a structure that is used for hearing airborne sound in extant tetrapods. The skull of C. morrisi also has several features associated with predatory behaviour, indicating that this dissorophid may have been one of the top terrestrial predators of its time.

Abstract: . The early Permian karst system near Richards Spur, Oklahoma preserves a diverse assemblage of terrestrial dissorophoid temnospondyls. Here we report the presence of a large-bodied dissorophine dissorophid that is represented by an articulated anterior trunk region, including a partial pectoral girdle, a ribcage characterized by extremely developed uncinate processes, and a rare, completely articulated pes. This represents the first documentation of the clade at the locality. Previously, dissorophids were represented only by the eucacopine Cacops. A complete pelvic girdle with hindlimbs is also referred to Cacops and represents the first material of the posterior trunk region to be described from the genus at Richards Spur. These specimens expand the taxonomic diversity known from the site and provide significant, well-preserved postcranial material that improves the characterization of dissorophid postcranial anatomy.