Brontotholus (meaning thunder dome) is an extinct genus of pachycephalosaur that lived in Late Cretaceous of Montana, U.S. and Alberta, Canada. The type species is Brontotholus harmoni.
Discovery and Naming[]
The holotype (MOR 480) was discovered by Bob Makela from the Two Medicine Formation of United States. It was mentioned as one of transitional pachycephalosaur, then uncatalogued, then it was assigned to Hanssuesia. In 2025, Woodruff and his colleagues described it as a new species. The generic name is based on a Mad Max movie (which is Mad Max: Beyond Thunderdome), and the type locality, while the specific name is named after Robert 'Bob' Harmon.
Description[]
All domes from Brontotholus have been discovered in Two Medicine Formation from United States except for TMP 1989.69.21, which is discovered in Canada, and it is tentatively referred to Brontotholus sp. Its body length is 3.8 meters (12ft), making it one of the largest pachycephalosaur from North America. It is a late subadult, which means its size could have been bigger when it reached the adult stage. Woodruff and his colleagues relied on morphological comparison to assume that it had a similar ontogenetic stage.
Classification[]
It is classified as a member of Pachycephalosauria. Its sister taxon is Foraminacephale brevis.
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