Allosauridae was a family of medium to large sized carnivorous theropod dinosaurs. Members included Saurophaganax, Allosaurus, and the poorly known Antrodemus, which could well be a specimen of Allosaurus.
The exact number of genera that can be included here is very debatable and most of the upper Jurassic and Lower Cretaceous carnosaurs are somewhat closely related to Allosaurus. Whatever the case, allosaurids seemed to be the most successful hunters of their times, outnumbering the Megalosauridae and Ceratosauridae, with which they competed for prey. The allosaurids would eventually be succeeded by their close relatives the carcharodontosaurids in the southern hemisphere, and replaced by the coelurosaurian tyrannosaurids in the northern hemisphere, during the Cretaceous Period.They wre 4.3 to 12 meters ( 14 to 40 ft).