Dinosaur genus

Brontotholus

Woodruff et al. 2025

Brontotholus is a dinosaur genus known from bones, found in rocks 83.6–72.2 million years old, in the United States and Canada.

Confidence labels

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At a glance

Data as of 11 October 2026

83.6–72.2 Ma

Triassic

Jurassic

Cretaceous

252 million years ago20114366

The last non-bird dinosaurs died out 66 million years ago. That's as far from us as the end of this bar.

Named by: Woodruff et al. 2025
medium
medium: Only PBDB gives this; nothing contradicts it.
Sources
Given by: Paleobiology Database. How it was chosen: PBDB leads.
Described in: D. C. Woodruff, J. R. Horner, M. B. Goodwin, D. C. Evans (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. Read it
medium
medium: Only PBDB gives this; its author and year match the naming authority (Woodruff et al. 2025).
Sources
Given by: Paleobiology Database. The publication the Paleobiology Database gives as the authority for this genus name, usually the one that first named and described it.
Type species: Brontotholus harmoni
medium
medium: Only PBDB gives this; nothing contradicts it.
Sources
Given by: Paleobiology Database. How it was chosen: PBDB leads.
Lived: Campanian, 83.6–72.2 million years ago
medium
medium: Only PBDB gives this; nothing contradicts it.
Omnisaura calculation83.6–72.2 million years ago, from its dated fossil records
medium
medium: Omnisaura's calculation from 4 confirmed PBDB records.
Sources
Given by: Paleobiology Database. How it was chosen: PBDB leads.
Fossils found in: United States
medium
medium: Only PBDB records it (3 records).
Canada
low
low: Only one PBDB record.
mixed
mixed: Levels differ between entries; each has its own.
Sources
Given by: Paleobiology Database. How it was chosen: Union of all sources (ISO 3166).
Rock formations: Two Medicine
medium
medium: Only PBDB records it (3 records).
Oldman
low
low: Only one PBDB record.
mixed
mixed: Levels differ between entries; each has its own.
Sources
Given by: Paleobiology Database. How it was chosen: Canonical names, automatic and editor-approved matches applied.
Family: Pachycephalosauridae
medium
medium: Only PBDB gives this; nothing contradicts it.
Sources
Given by: Paleobiology Database. How it was chosen: PBDB leads.
Parent group: Pachycephalosaurinae
medium
medium: Only PBDB gives this; nothing contradicts it.
Sources
Given by: Paleobiology Database. How it was chosen: PBDB leads.
Species named in its records: Brontotholus harmoni
Sources
Given by: Paleobiology Database (the species its fossil records are identified as).
Diet: herbivore (inferred for its group)
medium
medium: Only PBDB gives this, and it infers it for the whole of Ornithischia, the group this genus belongs to, not from this genus's own fossils.
Sources
Given by: Paleobiology Database. How it was chosen: PBDB, inferred from a group the genus belongs to.
Way of life: ground dwelling, gregarious (inferred for its group)
low
low: PBDB infers this way of life for the whole of Ornithischia; behaviour is rarely known for one genus.
Sources
Given by: Paleobiology Database. How it was chosen: PBDB, inferred from a group the genus belongs to.
Known from: Bones
Sources
Given by: Paleobiology Database (what the name was based on).

Sources: Paleobiology Database (CC BY 4.0)Confidence levels and gaps are Omnisaura's own assessment.

Gaps are answers

What isn't known yet

Order: no source we use gives it yet.
Common names: no source we use gives it yet.
What it was named after: no source we use gives it yet.
Resting on one source: 7 facts come from a single source with nothing against them (rated medium): name (PBDB); authority (PBDB); type species (PBDB); parent group (PBDB); family (PBDB); age (headline) (PBDB); diet (PBDB).

Size and appearance aren't covered yet, and diet and way of life only as PBDB infers them for the wider group. Omnisaura leaves the rest out rather than guess.

Where sources disagree

None open. Where our sources overlap, they agree on everything shown here.

Did it meet…?

Did Brontotholus meet ?

Same time, different places. Their fossils overlap in age, 83.6 to 72.2 million years ago, but no rock formation holds both.

Going by the ages and rock formations of their dated fossils, as on the map. Compare their fossil sites on the map.

Connections

Genera linked to Brontotholus by where and when their fossils were found, by classification and by who named them. Select a name to open its page.

Same rocks, same time 52

Genera found in the same rock units, from rocks of overlapping age, the most shared fossil sites first.

Saurornitholestes Troodon Richardoestesia Paronychodon Daspletosaurus Dromaeosaurus Hypacrosaurus Spheroolithus Continuoolithus Prismatoolithus Stenonychosaurus Struthiomimus Centrosaurus Maiasaura Monoclonius Oohkotokiaand 36 more

Same family: Pachycephalosauridae 6

Other genera in Pachycephalosauridae with a full profile.

Acrotholus Alaskacephale Amtocephale Colepiocephale Foraminacephale Sphaerotholus

Found in United States 82

Other genera found in United States, from rocks of overlapping age, the most fossil sites there first.

Saurornitholestes Stegoceras Agujaceratops Richardoestesia Kritosaurus Troodon Parasaurolophus Daspletosaurus Paronychodon Pentaceratops Gryposaurus Hypacrosaurus Ornithomimus Appalachiosaurus Orodromeus Utahceratopsand 66 more

Credits

Where this page comes from

Paleobiology DatabaseCC BY 4.0 · fossil records, ages, classification
OmnisauraOmnisaura editorial · confidence levels and gaps
PaleoMAP PaleoCoastlines (Kocsis and Scotese 2021)CC BY 4.0 · ancient coastlines on the small map
Natural EarthPublic domain · today's coastlines