Head study of the allosaurid Acrocanthosaurus. Before the tyrannosaurids were really the apex predators, towards the middle of the Cretaceous in North America, allosauroids were still the top predators. Pictured here is Acrocanthosaurus atokensis, from the southwestern portion of the United States. It ranged across what is now the great plains and the Texas desert. The most peculiar feature of this animal was its large ridge along its back, from which its name is derived.
