Paramacellodid lizard skulls from the Jurassic Morrison Formation at Dinosaur National Monument, Utah

New skull material of the Jurassic lizard Paramacellodus from the Morrison Formation of Dinosaur National Monument, Utah, permits a more comprehensive description of the anatomy of this lizard, previously known mainly from jaw and postcranial remains. The Morrison form cannot be satisfactorily distinguished from its British counterpart and the specimens are referred to Paramacellodus sp., cf. P. oweni. Cladistic analysis places Paramacellodus, and thus related genera attributed to the family Paramacellodidae Estes, 1983, as a sister taxon of Scincoidea (Cordyliformes + Scincidae), rather than of Cordyliformes alone.