Explore ancient mammalian history with this authentic 5.8″ Brontothere fossil knee bone, discovered in the Badlands of South Dakota. Dating back to the Eocene Epoch, this well-preserved specimen belonged to a Titanothere—an extinct relative of the modern rhinoceros. Its robust structure and natural detail make it a valuable addition for collectors, educators, and fossil enthusiasts. The fossil includes a Certificate of Authenticity and offers a glimpse into life over 35 million years ago. Available now at Fossil Age Minerals, your reliable source for genuine prehistoric fossils and specimens.