Small Fossil Turtle, Stylemys Tortoise, Badlands South Dakota, Oligocene, Z207

Description

Type:  This is a small turtle/tortoise of
Stylemys nebrascensis
. This is a partial turtle which has half of the top and all of the bottom of the shell preserved.  There is no restoration on this specimen. It will make a nice addition to the collection.
Weight: 15 ounces
Locality: Private land in Pennington County, South Dakota
Age: Oligocene, 30 Million Years Ago
Note that ruler increments are 1/16 inch.
Stylemys Tortoises
Tortoises and turtles
One of the most familiar and commonly preserved fossils in the White River Badlands are those of the land tortoises. Common in many levels, the best preserved and most commonly found one are in the oreodont beds of the Orellan NAMLA. Chadronian age specimens tend to be broken. Fossil land tortoises typically range in size from a few inches to as much as two feet in length, with the average size being 10 - 12 inches long. Due to the shape and structure of the shell, it is clear that they were land tortoises. Skeletal remains are also common although shells containing complete skeletons and the tortoise's skull are relatively rare. Fossils believed to be tortoise eggs are also occasionally found.
The most common variety of tortoise found is that of Stylemys nebrascensis, but other chelonians are occasionally found.  Aquatic turtles are far rarer in White River formations.  Although many collectors and paleontologists casually lump all Chadronian/Orellan tortoises into a single species, Stylemys nebrascensis, a number of paleoherpetologists now question this, feeling that based on shell shape, and even after taking post mortem shell deformation into consideration, that some species were relatively flat like our modern gopher tortoise of the Southeast and Southwest, while others were round and probably did not borrow. Similar niche separation is commonly observed in land tortoises of Africa and Asia.