Brontotholus
Sign in to saveBrontotholus () is an extinct genus of pachycephalosaurid dinosaur known from the Late Cretaceous (Campanian stage) Two Medicine and Oldman formations of Montana, United States, and Alberta, Canada, respectively. The genus contains a single species, Brontotholus harmoni, known from multiple partial domes.
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Brontotholus () is an extinct genus of pachycephalosaurid dinosaur known from the Late Cretaceous (Campanian stage) Two Medicine and Oldman formations of Montana, United States, and Alberta, Canada, respectively. The genus contains a single species, Brontotholus harmoni, known from multiple partial domes.
==Discovery and naming== The Brontotholus holotype specimen, MOR 480, was discovered in 1987 by Bob Makela from the Two Medicine Formation in Montana, United States. It was first mentioned as one of the transitional pachycephalosaurid specimens that are intermediate between Stegoceras and Pachycephalosaurus by Horner, Varricchio and Goodwin in 1992, then uncatalogued, and was subsequently assigned to cf. Hanssuesia sternbergi along with MOR 453 by Sullivan in 2003 prior to its 2025 redescription. The five known fossils of the Brontotholus material consist of frontoparietal domes, all discovered from the Two Medicine Formation except TMP 1989.69.21 found in 1989 by Wendy Sloboda from the Oldman Formation in Alberta, Canada.