Formation · Cretaceous
Judith River Formation
Late Cretaceous unit, Montana
The Judith River Formation is a Campanian river-plain unit of central Montana, roughly ten million years older than Hell Creek, famous for hadrosaur skeletons such as the Brachylophosaurus mummies and for shed tyrannosaur, dromaeosaur and Troodon teeth. It is the US extension of the Alberta Belly River Group, so faunas overlap with Dinosaur Provincial Park. Microsite teeth are inexpensive and abundant; complete skulls are rare and usually museum bound.
| Country | United States |
|---|---|
| Region | Montana |
| Age | Campanian, Late Cretaceous |
| Age range | ~79.5–75 Ma |
| Macrostrat rank | Fm· Macrostrat |
| Macrostrat age | 100–66 Ma· Macrostrat |
| PBDB collections | 114 collections, 592 occurrences· Paleobiology Database |
Collecting and legality
Commercial Judith River material comes from private land along the Missouri Breaks and near Malta and Havre; the Upper Missouri River Breaks National Monument (BLM) is closed to vertebrate collecting without a permit.
Lithology and setting
River-channel sandstones and floodplain mudstones with bentonite beds and coal, deposited as the Western Interior Seaway withdrew east.
Commonly recorded taxa (PBDB)
Genera most often recorded from this unit in the Paleobiology Database (first 200 occurrences): Meniscoessus (12), Alphadon (11), Mesodma (11), Stegoceras (10), Turgidodon (9), Cimolomys (8), Eodelphis (6), Filikomys (5), Gypsonictops (5), Hadrosauridae (5), Cimexomys (4), Protolambda (4), Theropoda (4), Boremys (3), Lepisosteus (3).
Source: Paleobiology Database
Collecting rules
Elsewhere
- Macrostrat: 71831
- macrostratConcept: 9025
- PBDB: strata:Judith River
- Wikidata: Q3077405
- Macrostrat stratigraphic name
- PBDB occurrences for this unit
- Wikipedia: Judith River Formation
- Mindat: Judith River Formation
Cite this article
Stratum Study. "Judith River Formation" (Formation). Stratum Study pack 2026.09, as of 2026-09-19. https://stratum.black/study/formations/judith-river-formation. Accessed 2026-09-20.
@misc{stratum-judith-river-formation,
title = {Judith River Formation},
author = {{Stratum Study}},
howpublished = {\url{https://stratum.black/study/formations/judith-river-formation}},
year = {2026},
note = {Formation article, Stratum Study pack 2026.09, as of 2026-09-19; sources: stratum, macrostrat, pbdb, wikidata, commons. Accessed 2026-09-20.}
} Citations carry the pack version and the article's as-of date so they resolve to the same text later. The facts themselves belong to the sources listed below; cite those for the science.