Andrewsarchus (Andrewsarchus Pao, 1923)
Temporal range: during the Eocene (Asia) (45—36 million years ago)
Dimensions: length - 3,2 m, height - 140 сm, weight ~ 800 kg
A typical representative: Andrewsarchus mongoliensis Osborn, 1924
Andrewsarchus mongoliensis, was a mammal that lived during the Eocene epoch, roughly between 45 and 36 million years ago. It had a long snout with large, sharp teeth and flat cheek teeth that may have been used to crush bones. Because Andrewsarchus is only known from a single skull, whether it was an active predator or a large scavenger is open to debate, as is its exact time range. Andrewsarchus is known only from an enormous skull (83 cm long and 56 cm wide) and pieces of bone. If Andrewsarchus was proportioned in the same manner as Mesonyx obtusidens, it had a length from the snout to the back of the pelvis of about 3.4 m and a height from the ground to the shoulder or middle of the back of about 1.8 m. Thus in round numbers it is possible that it may have been three times the size of Synoplotherium (Dromocyon) vorax or of Mesonyx obtusidens and possibly the largest land-dwelling carnivorous mammal known. Its chief rival for this title is the South American short-faced bear Arctotherium, which is estimated to have weighed up to 1,700 kg . The cranium is about twice the length of that of a modern Alaskan brown bear (Ursus arctos middendorffi), but with a lower length-to-width ratio, and about triple the length of an American wolf's (Canis occidentalis). With modern brown bears or polar bears weighing between 450 kg and 675 kg and only an extreme specimen of a wolf weighs up to 77 kg, this plausibly puts Andrewsarchus in the 1,000 kg size range. This weight appears close to the practical size limit of carnivorous land mammals, possibly relating to available food as well as metabolic requirements.