New data on the cranial anatomy ofLycaenops(Synapsida, Gorgonopsidae), and reflections on the possible presence of streptostyly in gorgonopsians

Study of a skull attributed to Lycaenops angusticeps reveals the presence of a ventral flange of the jugal that supports the transverse flange of the pterygoid. The quadrate was apparently not streptostylic, contrary to previous reports because its articulation with the epipterygoid and the pterygoid would only allow slight bending and because extensive movement of the quadrate would have been accompanied by similar movements of the stapes. Several characters previously used to argue for streptostyly of the gorgonopsian quadrate are primitive characters that were present in Permo-Carboniferous synapsids. The reduction of the contact between quadrate and pterygoid may have been selected for improved hearing of air-borne sounds. The reflected lamina was possibly involved in the reception of air-borne sounds (if gorgonopsians could detect them), along with the tympanum.