Little Bighorn Battlefield's Plesisaur

Do you know what lies underneath your feet?

The Upper Cretaceous Period ranges from (100 million to 65.5 million years ago) and represents the mud and sand that was originally deposited in a seaway that now makes up a part of the bedrock that underlies Little Bighorn Battlefield National Monument.

In 1977, a routine grave excavation in the Custer National Cemetery turned out to be anything but. A backhoe operated by National Park Service maintenance employee, exhumed the fossil remains of a partial marine reptile, the short-neck Plesiosaur (Dolichorhynchops osborni)! A marine reptile that lived from the end of the Triassic Period 220 million years ago to the end of the Cretaceous Period 60 million years ago.


A nearly complete vertebral column, complete pectoral girdle, complete pelvic girdles were collected after six days of after-hour volunteer work by park staff and local paleontologists, Russell King, and Alan Tabrum. The skeleton was disarticulated and penetrated by plant roots, but overall fairly well preserved.

The specimen was on display in the Smithsonian’s Life in the Ancient Seas exhibit in May of 1990 when the exhibit opened. Missing items from this specimen, such as the paddles and skull, were provided by the Museum of Paleontology at University of California Berkley. This specimen was removed in 2013 when the exhibit closed, but it is still mounted in collections.

Last updated: June 29, 2017

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