Osteology of the large dissorophid temnospondyl Anakamacops petrolicus from the Guadalupian Dashankou Fauna of China

Abstract

ABSTRACTDissorophidae are terrestrial temnospondyls with conspicuous armor. All known Guadalupian dissorophid species, including Anakamacops petrolicus, are established based on incomplete materials. Here two new dissorophid specimens from the Guadalupian Dashankou Fauna of China are described and referred to A. petrolicus. They provide much more new osteological information of this species. Anakamacops petrolicus has the largest skull among all known dissorophid species. It exhibits knobby exostoses on the skull roof and mandible, a high suborbital bar that is greater than half of the skull height, a triangular, posteriorly closed otic notch with the anteroposterior length greater than the width, relatively smooth vomer with a few denticles on the lateral margin, two nuchal (occipital) ridges with short overlap where the right one is anterior to the left one, the interpterygoid vacuity far from the choana, low coronoid process, the medial ridge of the adductor fossa close to the ventral margin of the mandible, and the first inner osteoderm nearly triangular with concave margins in dorsal view. The Guadalupian dissorophid species form a monophyletic clade, Kamacopini, which was distributed in northeastern Pangaea, with the following synapomorphies to differentiate it from other dissorophids: suborbital bar high (subequal to or greater than the orbital height) and the interpterygoid vacuities far from the choanae.