brontotheres

Brontotheres were a group of extinct, large, herbivorous mammals that lived from the Eocene to the Oligocene epochs, roughly 56 to 23 million years ago. They are often referred to as "thunder beasts" due to their imposing size, with some species reaching the dimensions of a rhinoceros or even a small elephant. Brontotheres belonged to the extinct order Embrithopoda, though their exact evolutionary relationships have been debated. They are most closely related to hyraxes and possibly elephants and sirenians.

The most distinctive feature of many brontotheres was a large, horn-like protuberance on their snout. In some species, this was a single, blunt horn, while in others, it was a pair of smaller, more flattened structures. These structures were likely made of bone covered in skin, rather than true keratinous horns like those of modern bovids. The function of these horns is uncertain, but theories include defense against predators, combat between males for mates, or even display.

Brontotheres were widespread, with fossils found in North America, Europe, and Asia. They were grazers or browsers, feeding on vegetation. Their extinction is thought to be linked to climate change, particularly the cooling and drying trends of the Oligocene, which led to the decline of their preferred forest and woodland habitats and the rise of grasslands. Despite their impressive size and unique features, brontotheres left no living descendants.