Allosauroidea is made up of two groups of dinosaurs the Allosauridae, which includes the Late Jurassic Allosaurus; and the Carcharodontisauridae, which includes Carcharodontosaurus, from the middle Late Cretaceous of Niger. Sinraptor, from the Middle Jurassic of China, and some other related forms may be carcharodontosaurids, but additional fossil material is needed to help resolve their position within Allosauroidea. Sinraptor is one of the earliest known allosauroids and Carcharodontosaurus is one of the latest.
Many allosauroids had fairly good-sized forelimbs, unlike the Tyrannosauridae (within Coelurosauria). They also tended to have long, narrow skulls with either horns or some kind of crest, large orbits, and three-fingered manus (hands).
Allosaurus fragilis (left) is the archetypal allosauroid, and probably the second most fashionable theropod dinosaur next to T. rex. Allosaurs had large, narrow jaws, fairly long and well-muscled forelimbs with huge claws, and large legs ending in heavy, clawed feet. UCMP has the cast of a mostly complete specimen that was formerly mounted at the California Academy of Sciences in San Francisco. Allosaurids were probably fierce hunters, able to grab prey with their clawed arms and rip it to shreds with their great jaws. It is possible that the taloned hind limbs were used to dispatch large prey as well, but all of this is merely conjecture. The Allosauridae existed mostly in the Jurassic period and were succeeded by their close relatives, the carcharodontosaurids.
The Carcharodontosaurids, along with spinosauroids, were the dominant predators throughout much of the world during the Early and Middle Cretaceous, but about 25 or 30 million years before the end of the Cretaceous, the carcharodontosaurids disappeared and were replaced by tyrannosaurids in North America, and abelisaurids (neoceratosaurids) elsewhere.
Portions of this page created by John Hutchinson 11/1995; modifications and additions since 2005 by David Smith. Allosaurus photo courtesy of Don Lofgren, Raymond M. Alf Museum.