Cacops woehri

Cacops (Greek for "blind face" ), a genus of dissorophid temnospondyls, is one of the most distinctive Paleozoic amphibians that diversified in the equatorial region of Pangea during the Kungurian stage of the early Permian. Dissorophids were a group of fully terrestrial, often heavily armored faunivores. This, along with their relatively large size and geographical range suggest that they were able to coexist with amniotes as predators during the early Permian. Dissorophidae has four distinct clades differentiated largely on the morphology of the osteoderms, the Eucacopinae (previously Cacopinae), the Dissorophinae, the Aspidosaurinae, and the Platyhystricinae. Cacops is one of the few olsoniforms (dissorophids and the larger trematopids) whose ontogeny is beginning to surface. Cacops fossils were almost exclusively known from the Cacops Bone Bed of the Lower Permian Arroyo Formation of Texas for much of the 20th century. New material collected from the Dolese Brothers Quarry, near Richards Spur, Oklahoma in the past few decades has been recovered, painting a clearer picture of what the animal looked and acted like.

American paleontologist Samuel W. Williston used the details of the species Cacops aspidephorus to first describe its features. However, because of the poor preservation of specimens collected from the Cacops Bone Bed in Texas, other researchers who collected specimens from other localities have described many of Cacops’ features with more certainty. Features that distinguish Cacops from other dissorophids include a large dorsal process of the quadrate and a shortened posterior skull. The skull is very box-like and its cheeks aligned almost at a right angle to the skull table. The external cranial ornamentation is noticeable on the skull table and on top of the ridges that border the numerous depressions. One significant ontogenetic change in Cacops is a more evenly distributed ornamentation in the adults. Like other dissorophids, the temporal region of Cacops’ skull was dominated by the tympanic embayment, which likely housed a large tympanum. Marginal teeth are recurved and thinner than in other temnospondyls. Cacops has fewer, but larger, teeth than in most other dissorophids. The palatal dentition consists of recurved tusks larger than the marginal teeth and minute, strongly recurved teeth that cover most of the palatal surface. Cacops was a medium-sized dissorophid, being smaller than later dissorophids from Eurasia such as Kamacops. Like other dissorophids, Cacops had osteoderms associated with the vertebral column. Internal osteoderms are fused to the neural spines, while external osteoderms overlapped adjacent positions with a ventral flange that inserted between successive internal osteoderms. The osteoderms are associated with only the first 15 vertebrae, beginning at the axis. They are relatively narrow, especially posteriorly, and are subrectangular in dorsal profile, except for the first osteoderm which is more triangular. The osteoderms also have dermal pitting on their dorsal surfaces. The distributions of these …