Triceratops, a dinosaur recognized by its distinctive three-horned face, roamed the Earth during the Late Cretaceous period, approximately 68 to 66 million years ago. Its fossil record provides insights into the ecosystems of that ancient time. Studying the distribution of Triceratops fossils helps scientists understand the geography and biodiversity of the Late Cretaceous world.
North American Home
Triceratops fossils have been found exclusively in western North America. During the Late Cretaceous, this region was part of a landmass called Laramidia, a large island continent separated from eastern North America (Appalachia) by the Western Interior Seaway. This shallow sea stretched from the Gulf of Mexico to the Arctic Ocean, dividing the continent for millions of years.
Laramidia’s distinct geography, with a narrow belt of plains nestled between the seaway and the emerging Rocky Mountains, influenced the evolution and distribution of many dinosaur species, including Triceratops. This unique geography led to distinct dinosaur assemblages across Laramidia.
Key Geological Formations
A geological formation is a body of rock layers with distinct characteristics that allow it to be mapped. Triceratops fossils are commonly found in several significant Late Cretaceous geological formations across western North America. These formations represent ancient environments conducive to the preservation of large dinosaur remains.
The Hell Creek Formation is a particularly rich source of Triceratops fossils, stretching across parts of Montana, North Dakota, South Dakota, and Wyoming. This formation consists of fresh and brackish-water clays, mudstones, and sandstones, indicating deposition in fluctuating river channels, deltas, and occasional swampy lowlands along the Western Interior Seaway’s margin. The Hell Creek Formation is estimated to have been deposited over about 2 million years, ending around 66 million years ago.
Another important site is the Lance Formation, located in eastern Wyoming, which is considered geologically equivalent to the Hell Creek Formation. Its sediments were laid down by streams on a coastal plain along the seaway’s edge, characterized by a subtropical climate with ample precipitation.
In Canada, Triceratops fossils have been discovered in the Scollard Formation in Alberta and the Frenchman Formation in Saskatchewan. These formations also represent ancient coastal plain environments, similar to their counterparts south of the border.
Unearthing Ancient Giants
Triceratops fossils have been unearthed in various states and provinces across its North American range. In the United States, Montana is particularly known for its abundance of Triceratops remains within the Hell Creek Formation. Over 50 Triceratops skulls have been collected from this formation, providing detailed insights into the genus’s evolution. The largest Triceratops skull ever found, nicknamed ‘Dragon King,’ was discovered in Glendive, Montana.
Wyoming has also yielded numerous Triceratops fossils, especially from the Lance Formation. Recent excavations in northeastern Wyoming have uncovered multiple Triceratops skeletons, including some of the most complete specimens ever found. One dig in Wyoming uncovered over 1,200 bones and fragments from at least five Triceratops individuals.
South Dakota and North Dakota are other states where Triceratops remains are common, primarily within the Hell Creek Formation. In South Dakota, a 3,000-pound Triceratops skull was unearthed in the Badlands, while another, named ‘Big John,’ was found in Perkins County. Colorado has also contributed to the fossil record, with Triceratops bones found near Denver and Thornton, including notable skull discoveries.
Canadian provinces, including Saskatchewan and Alberta, have also revealed Triceratops fossils, though they are less common there than in the United States. A significant discovery in Alberta was a well-preserved Triceratops skull, nicknamed “Calli,” found in the foothills of southwestern Alberta.