A group of scientists led by Cameron Pal and Louis Ruedas of Portland State University in their new work argues that Allosaurus - a genus of large theropods of the Jurassic period - were not predators, but scavengers.
Allosaurus were contemporaries of some of the largest herbivorous dinosaurs ever recorded. This included well-known dinosaurs such as Camarasaurus, Barosaurus, Apatosaurus, Diplodocus, Brontosaurus, Supersaurus, and Brachiosaurus. Brachiosaurus, in particular, was once considered the largest land animal that ever lived, and could reach 20 meters in length and 64 tons in weight.
When these giant dinosaurs died of natural causes - disease, hunger and weakness, which is typical of many modern herbivorous populations, their carcasses were enough to support viable populations of allosaurs even without hunting.
The researchers supported this hypothesis with a robust agent-based model that modeled the relationship between carcass resources present in the Morrison Formation resulting from the death of these sauropods and the Allosaurus' food energy requirements.
They also studied skull morphology, including the degree of binocular vision in predators versus scavengers, as well as ecological data from fossils, such as the relative population size of carnivores, herbivores, and scavengers.
The relative fragility of the skull and teeth of Allosaurus already cast doubt on the fact that these animals were predators. In addition to this disadvantage, Allosaurus did not have the binocular vision required for a successful predator: the degree of its binocular vision was only 30% similar to that of Tyrannosaurus rex and was only 15% of that of a modern lion.
Allosaurus walked on two legs, had a large head and jaws full of long, sharp teeth that easily fell out and were constantly renewed. Also, like the T-Rex, they had small shoulders and forepaws. Together, these characteristics and external similarity to T. rex led to the fact that Allosaurus began to be considered the main predator of the Late Jurassic.
The researchers note that this stereotype now needs to be revisited, since allosaurs played an ecological role as scavengers, like today's vultures, and were not active predators.