Size and Weight:
Considering that all we know about Andrewsarchus is based on a single, incomplete skull discovered in the Gobi Desert almost 100 years ago, on an expedition led by the famous paleontologist Roy Chapman Andrews, this prehistoric mammal has made quite a reputation for itself. Based on well-informed reconstructions--guided by similarities with its close relative, the North American Mesonyx--Andrewsarchus may have been the largest carnivorous land mammal that ever lived, its 13-foot length and 1,000 to 2,000-pound weight putting it in a different class entirely than modern polar or grizzly bears. (Still, Andrewsarchus would have been a mere snack for the truly gigantic carnivorous dinosaurs, like the seven-ton Tyrannosaurus Rex, that preceded it by 30 million years.)
As little was we know about what Andrewsarchus looked like, we know even less about how this late Eocene predator behaved. Andrewsarchus may or may not have hunted in packs, and it may or may not have supplemented its diet of fresh-killed meat by scavenging already-dead carcasses (yet another parallel with the extinct T. Rex). So huge and powerful were its jaws that, conceivably, Andrewsarchus might have been able to bite through shelled mollusks or turtles, and it may even have supplemented its carnivorous diet with the occasional plant. One likely scenario is that Andrewsarchus fed on the enormous, herbivorous brontotheres (poster genus: Brontotherium) that shared its Eurasian habitat.