The first pachycephalosaurid from the Late Cretaceous Two Medicine Formation: effects of the Western Interior Seaway on North American pachycephalosaurid evolution

Citation

Woodruff, D. C.; Horner, J. R.; Goodwin, M. B.; Evans, D. C. (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). Oxford University Press (OUP). doi:10.1093/zoolinnean/zlaf087

Names first published here

• Brontotholus genus
• Brontotholus harmoni species

Cited by genera

• Amtocephale

  Recovered Amtocephale in a basal polytomy of Pachycephalosauridae.

• Brontotholus
• Hanssuesia

  Agrees with Dyer and colleagues (2023) that it is probably a synonym of Stegoceras validum, but scores it as a separate terminal pending an ontogenetic study; recovers it as sister to Colepiocephale.

• Homalocephale

  Leaves it unresolved within Pachycephalosauridae, paired with Goyocephale.

• Stegoceras

  Concurs with the synonymy of Gravitholus, and holds Hanssuesia pending a fuller ontogenetic assessment.

• Texacephale

  Excluded it from its phylogenetic analysis because the holotype is taphonomically distorted, and questioned its validity.