Formation · Cretaceous

Hell Creek Formation

Late Cretaceous unit, Montana · North Dakota · South Dakota · Wyoming

The Hell Creek Formation is the last dinosaur-bearing unit of the Late Cretaceous in the northern Great Plains, ending at the K–Pg boundary 66 million years ago. It supplies most of the Triceratops, Tyrannosaurus and Edmontosaurus teeth, bone and frill fragments in trade, alongside shed crocodile and champsosaur teeth, turtle shell and the guitarfish Myledaphus from microsites. Buyers should expect gap-fill and stabilisation on bone, and should insist on the county and ranch of origin, since sale of vertebrate material from federal land is illegal.

Country	United States
Region	Montana, North Dakota, South Dakota, Wyoming
Age	Maastrichtian, Late Cretaceous
Age range	~68–66 Ma
Group	Montana Group
Macrostrat rank	Fm· Macrostrat
Macrostrat age	100–56 Ma· Macrostrat
PBDB collections	597 collections, 5526 occurrences· Paleobiology Database

Collecting and legality

Most commercial Hell Creek material comes from private ranches in Garfield, McCone and Dawson counties (Montana) and the Dakotas, collected under written landowner agreements. Vertebrate fossils on BLM and other federal land need a research permit and cannot be sold; casual collecting there is limited to common invertebrates and plants. Ask for the ranch name and the agreement, and record the county on every specimen.

Lithology and setting

Fluvial sandstones, siltstones and carbonaceous mudstones deposited on a coastal plain west of the retreating Western Interior Seaway; lignite beds and the Fort Union contact mark the K–Pg boundary at the top.

Commonly recorded taxa (PBDB)

Genera most often recorded from this unit in the Paleobiology Database (first 200 occurrences): Meniscoessus (19), Gypsonictops (15), Mesodma (15), Protolambda (15), Cimolodon (12), Didelphodon (10), Glasbius (10), Leptalestes (9), Pediomys (9), Alphadon (8), Essonodon (7), Cimolomys (4), Amia (2), Batodon (2), Cimolestes (2).

Source: Paleobiology Database

Elsewhere

Cite this article

Stratum Study. "Hell Creek Formation" (Formation). Stratum Study pack 2026.09, as of 2026-09-19. https://stratum.black/study/formations/hell-creek-formation. Accessed 2026-09-20.

BibTeX · CSL-JSON

@misc{stratum-hell-creek-formation,
  title        = {Hell Creek Formation},
  author       = {{Stratum Study}},
  howpublished = {\url{https://stratum.black/study/formations/hell-creek-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.

Collecting and legality

Lithology and setting

Commonly recorded taxa (PBDB)

Age

Localities

Collecting rules

Typical taxa

Referenced by

Elsewhere