2.4" Brontothere Fossil Femur Bone Eocene Age Badlands S Dakota Titanothere COA

Location: White River Badlands, South Dakota

Weight: 4.7 Ounces

Dimensions: 2.4 Inches Long, 2.4 Inches Wide, 2.2 Inches Thick (Matrix)

Eocene Age, 56 to 33.9 million years Old.

Comes with a Certificate of Authenticity.

The item pictured is the one you will receive. 

Brontotheres were ancient mammals that inhabited the region now known as Badlands National Park between approximately 56 and 33.9 million years ago. In scientific literature, Badlands brontotheres are classified as Megacerops coloradensis. They are sometimes referred to as “titanotheres,” a name meaning “thunder beasts”—a nod to the thunderous sound a herd of these massive animals would have made as they moved across prehistoric landscapes.

Brontotheres found in the Badlands would have stood about 8 feet tall and measured up to 16 feet long, comparable in size to a modern large rhinoceros or a small elephant. However, these giants did not start this way. Early brontotheres from the beginning of the Eocene epoch were only dog-sized. Over the following 20 million years, they underwent significant evolutionary changes—growing larger, diversifying into multiple species, and eventually reaching the massive proportions represented in late Eocene Badlands brontothere fossils.

One of the most distinctive features of brontotheres is their paired blunt horns, positioned above the nose. These structures began as small bumps in early species but eventually evolved into large, forward-projecting horns that could extend more than 3.3 feet (1 meter) in the Badlands forms. As with many horned mammals, these horns were typically larger in males and smaller in females. While their appearance naturally evokes comparisons to modern rhinos, brontotheres were not their direct ancestors. However, true early rhinoceroses—such as Subhyracodon—do appear in the Badlands fossil record, representing genuine members of the rhino family.