Dinosaurs A to Z
Pachycephalosauridae

Brontotholus harmoni

"thunder dome"

Generic pachycephalosaur body-plan outline
You 1.8 m (5.9 ft) tall
Brontotholus 3.8 m (12.5 ft) long
as long as 3 people standing fingertip to fingertip
generic pachycephalosaur body plan, scaled to length — not a silhouette of Brontotholus
Length
3.8 m (12.5 ft)
Period
Late Cretaceous (75.5–75.3 Mya)
Place
United States · Canada · Alberta, Canada · Montana, USA
Food
Herbivore
Clade
Pachycephalosauridae Dinosauria Ornithischia Cerapoda Marginocephalia Dome-headed bipedal herbivores.
Brontotholus reconstruction by Connor Ashbridge
Reconstruction · Connor Ashbridge (CC-BY)

Brontotholus (“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.

What we know

  • Named by Woodruff et al., 2025.
  • Body length estimated at about 3.8 m.
  • Fossils found in United States and Canada.

What we guess

The reconstruction notes for Brontotholus — soft tissue, color, behavior — haven't been written up yet. Only the recorded basics above are filled in so far.