Andrewsarchus

Andrewsarchus mongoliensis is an extinct genus of mammal that lived during the middle Eocene epoch, approximately 45 to 36 million years ago. It is known from a single, massive skull discovered in the Irdin Manha Formation of Inner Mongolia, China. The most striking feature of Andrewsarchus is its enormous skull, measuring about 83 centimeters (33 inches) in length. This size suggests that Andrewsarchus was one of the largest mammalian land predators ever to have lived. However, the fragmentary nature of the fossil remains means that its exact classification and lifestyle remain a subject of debate among paleontologists.

Initially, it was thought to be a kind of mesonychid, an extinct group of hoofed mammals. More recent analyses, based on dental and cranial features, have suggested a closer relationship to artiodactyls, the even-toed ungulates, possibly as a basal member of the cetancodontamorpha, a group that includes whales, hippos, and anthracotheres. The broad, flat snout and large teeth suggest a diet that may have included meat, but its exact feeding habits are speculative. Some theories propose it was an opportunistic scavenger or omnivore. Its sheer size and the discovery location in what was likely a floodplain environment have led to reconstructions of a formidable, wolf-like or bear-like creature, though its body proportions are entirely unknown. The name honors the American paleontologist Roy Chapman Andrews.