Brontotholus
| Brontotholus | |
|---|---|
Scientific classification 
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| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Clade: | †Ornithischia |
| Clade: | †Pachycephalosauria |
| Family: | †Pachycephalosauridae |
| Genus: | †Brontotholus Woodruff et al., 2025 |
| Species: | †B. harmoni
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| Binomial name | |
| †Brontotholus harmoni Woodruff et al., 2025
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Brontotholus (lit. 'thunder dome') 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
[edit]The Brontotholus holotype specimen, MOR 480, was discovered in 1987 by Bob Makela from the Two Medicine Formation in Montana, United States.[1] 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,[2] and was subsequently assigned to cf. Hanssuesia sternbergi along with MOR 453 by Sullivan in 2003 prior to its 2025 redescription.[3] 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.[1]
In 2025, Woodruff and colleagues described Brontotholus harmoni as a new genus and species of pachycephalosaurs based on these fossil remains. The generic name, Brontotholus, is a combination of Ancient Greek words βροντή (brontē, "thunder") and θόλος (tholos, "dome") based on the 1985 film Mad Max Beyond Thunderdome and the locality name "Beyond Thunder Dome" where the paratype was discovered. The specific epithet, harmoni, is named in honour of the late Robert 'Bob' Harmon, a former fossil preparator at the Museum of the Rockies. Only two specimens (the holotype MOR 480 and the paratype MOR 479) are definitively referred to B. harmoni, while the other three specimens (MOR 453, MOR 550 and TMP 1989.69.21) are tentatively referred to the genus as B. sp.[1]
Description
[edit]
The holotype of Brontotholus is estimated to have reached a body length of 3.8 metres (12 ft), making it the third largest North American pachycephalosaurid after Pachycephalosaurus and Platytholus. MOR 453 is the largest specimen referred to the genus Brontotholus, identified as a late subadult based on osteohistological analysis. Woodruff and colleagues relied on morphological comparison to assume that the holotype reached a similar ontogenetic stage, as they were unable to obtain high-resolution CT scans or perform osteohistological analyses based on known fossil material.[1]
Classification
[edit]Woodruff et al. (2025) recovered Brontotholus as a sister taxon of Foraminacephale within the Pachycephalosauridae polytomy. The results of the strict consensus phylogenetic analysis based on extended implied weighting is displayed in the cladogram below:[1]
| Pachycephalosauridae |
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References
[edit]- ^ a b c d e Woodruff, Cary D; Horner, John R; Goodwin, Mark B; Evans, David C (October 9, 2025). "The first pachycephalosaurid from the Late Cretaceous Two Medicine Formation: effects of the Western Interior Seaway on North American pachycephalosaurid evolution". Zoological Journal of the Linnean Society. 205 (2) zlaf087. doi:10.1093/zoolinnean/zlaf087. ISSN 0024-4082.
- ^ Horner, John R.; Varricchio, David J.; Goodwin, Mark J. (1992). "Marine transgressions and the evolution of Cretaceous dinosaurs". Nature. 358 (6381): 59–61. Bibcode:1992Natur.358...59H. doi:10.1038/358059a0. S2CID 4283438.
- ^ Robert M. Sullivan (2003). "Revision of the dinosaur Stegoceras Lambe (Ornithischia, Pachycephalosauridae)". Journal of Vertebrate Paleontology. 23 (1): 181–207. doi:10.1671/0272-4634(2003)23[181:rotdsl]2.0.co;2.
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