Fossils of the Lewis and Clark Expedition

The Saurocephalus lanciformis fossil found by Patrick Gass. Last known to be within the collection of the Academy of Natural Science at Drexel University, Philadelphia.

Lewis and Clark collected a huge amount of material that was either shipped back to Washington City, or was carried back with the Corps. But the number of fossils found by the Corps was negligible. While very little is mentioned in the journals about fossils, the explorers did find a few and made a few observations.

The first fossil they came across was found by Patrick Gass on August 6, 1804. It’s the one fossil known to survive today from the Expedition, although it’s specific location is not known. While he did not mention it in his journal (nor did any of the other journal writers), the information was recorded by Lewis on a tag that accompanied the specimen back to President Jefferson in the spring of 1805 from Fort Mandan. Gass's discovery was near Soldiers River, which flows in today’s Harrison County, Iowa, from strata dated to the Cretaceous Period. The original label indicates that it was collected in a "cavern," but since no caves are mentioned at this point by the journalists, it may have been an undercut in the bank or deep ravine along the river.

The label, written by Lewis, reads: "Petrifed Jaw bone of a fish or some other anamal found in a cavern a few miles distance from the Missouri S side of the River. 6 Aug. 1804." The fossil is a fragmentary right upper jaw, black, with a few small, sharp, beveled teeth. About 20 years after the expedition it was finally identified as a new genus and species of fossil fish, Saurocephalus lanciformis" – a spear-shaped lizard-head.

About a month later, on September 10, 1804, while in today’s southeastern South Dakota, another fossil was found – a huge back bone of an aquatic reptile, nearly 45 feet long.