Dino card No. 0311 of 2,015

Brontotholus

Say it: bron-TOE-tho-lus

Name means: “thunder dome”1

Ate: PlantsDome-headsLate Cretaceous

Brontotholus was a dome-headed dinosaur that lived about 75 million years ago. It walked on two legs and had a thick, bony dome on its skull. This dinosaur was a plant-eater and one of the biggest dome-headed dinosaurs in North America.1 2

Lived

84 to 72 million years ago3

Late Cretaceous

Fossils found in

Montana, USA and Alberta, Canada3 1

Food

Plants3

Length

3.8 m1

estimate for the holotype, the largest known specimen may have been bigger

Artist's life restoration of Brontotholus — How Brontotholus may have looked, by Connor Ashbridge. CC BY 4.0, via Wikimedia Commons. Scientists still argue about colours and details.

When did it live?

Triassic

Jurassic

Cretaceous

252 million years ago20114566, the asteroid

How big was it?

cool stuff

Fun facts

Brontotholus is the third largest dome-headed dinosaur known from North America, after Pachycephalosaurus and Platytholus.1

Its name comes from the 1985 movie Mad Max Beyond Thunderdome, because one fossil was found at a place called 'Beyond Thunder Dome'.1

The first fossil of Brontotholus was found in 1987 by Bob Makela in Montana.1

Scientists know Brontotholus mostly from its skull domes, because the rest of the skeleton is rarely preserved.2

Brontotholus lived during the Late Cretaceous period, about 75 million years ago.1 2

This dinosaur was a plant-eater, even though its thick dome might make it look like a fighter.3

The species name harmoni honors Robert 'Bob' Harmon, a fossil preparator at the Museum of the Rockies.1

Myth buster

Myth: Dome-headed dinosaurs like Brontotholus used their domes for head-butting each other.

Truth: Scientists are not sure. Some think the domes were for display or species recognition, not for fighting.1

For dino experts

Scientific name: Brontotholus
Named by: Woodruff et al. 20253
Group: Dome-heads
Family / clade: Pachycephalosauridae3
Classification: Ornithischia > Pachycephalosauria3
Age of the rocks: 84 to 72 million years (Campanian)3
Rock formations: Two Medicine, Oldman3
Countries: USA, Canada3
Fossil records: 4 in the Paleobiology Database3
Discovery: Brontotholus was named in 2025 by Woodruff, Horner, Goodwin and Evans. The first fossil was found in 1987 in Montana, but it took many years before scientists realized it was a new species.1
Still debated: Scientists are not sure if all five fossils belong to Brontotholus or if some might be other dome-headed dinosaurs.1

Where the facts come from

Brontotholus (en.wikipedia.org)
New species of dome-headed dinosaur discovered in Montana - ABC News (abcnews.com)
Brontotholus in The Paleobiology Database (CC BY 4.0): age, places, rock formations, classification.

Every fact on this page has a number that points to its source. If we got something wrong, sorry, we are dino fans, not a science journal. Tell us at [email protected] and we will fix it.