6.7" Inflated Fossil Tortoise (Stylemys) - South Dakota

Inflated Fossil Tortoise (Stylemys) - South Dakota #192061

This is a stunning, 6.7" long specimen of an Oligocene age tortoise (Stylemys sp.), collected from the White River Formation in Pennington County, South Dakota. The shell remained quite inflated with relatively little crushing and wonderful preservation. Both the carapace and plastron are present on this gorgeous specimen, though the connection points between each required some restoration. The nuchal scute and about 4 of the anterior marginal scutes have been restored, along with a lateral (left side) marginal scute.

The majority of the tortoise fossils from this site are those of the species Stylemys nebrascensis. This specimen however is much taller/rounder than S. nebrascensis and is from a less abundant species. While it's debated as to whether S. nebrascensis could burrow based on their flatter shell, it's very likely that this species, with its tall shell, did not burrow.

Stylemys ("pillar turtle") is the first fossil genus of dry land tortoise discovered in the United States. They lived in temperate to subtropical areas of North America, Europe, and Asia.

These extinct tortoises had primitive jaw muscles, unlike today's tortoises that also display the os transiliens bone, and would have been herbivorous. While Stylemys species did exhibit the same neck structure as modern tortoises, the forelimbs weren't ideal for burrowing.