Allosaurus modernus is a large bipedal predator that is almost entirely featherless, being mostly covered in scales, but it has some small loose feathers on the back of its head and neck. Its skull is large and equipped with dozens of sharp, serrated teeth. Its size averages around 9.5 metres (31 feet) in length and weigh about 4 tons, though some individuals have reached over 12 metres (39 feet) and weigh about as much as 5.8 tons, and some of these big Allosaurus modernus are still alive today. Relative to the large and powerful hindlimbs, its three-fingered forelimbs are small, and the body is balanced by a long and heavily muscled tail. As the most abundant large predator in the Morrison Formation in the original Allosaurus species, it was at the top of the food chain, liked preyed on contemporaneous large herbivorous dinosaurs, and perhaps even other predators, but today, they feed on live and/or dead domestic pigs, domestic goats, and/or domestic cattle. Allosaurus modernus normally has cooperative social behavior and are known to hunt in packs, however, some individuals are solitary can be aggressive toward each other (although most solitary Allosaurus modernus are nonaggressive and can congregate where there's a big carcass) and thus are kept seperated from social Allosaurus modernus.