Platytholus is an extinct genus of pachycephalosaurid dinosaur from the Late Cretaceous (Maastrichtian) Hell Creek Formation of the United States. The genus contains a single species, P. clemensi, known from a partial skull.[1]
The Platytholus holotype specimen, MOR 2915, was discovered during the early 2000s in sediments of the Hell Creek Formation, dated to the latest Maastrichtian age of the late Cretaceous period, in Garfield County, Montana. The specimen consists of a partial skull.[1]
In 2023, Horner, Goodwin & Evans described Platytholus clemensi, a new genus and species of pachycephalosaurid, based on these fossil remains. The generic name, "Platytholus", combines the Latinised Greek "platys", meaning "flattened", "wide", or "broad", and "tholos", meaning a "small domed hill". The specific name, "clemensi", honors American paleontologist William A. Clemens Jr.[1]
Horner, Goodwin & Evans (2023) recovered Platytholus as a pachycephalosaurine member of the Pachycephalosauridae, as the sister taxon to a clade formed by Prenocephale and Acrotholus. The results of their phylogenetic analyses are shown in the cladogram below:[1]