Allosaurus

Characteristics ~ ~ ~ ~

Allosaurus is the premier theropod of the Jurassic and is considered to be the lion of its time, averaging 28 feet long and 2.5 tons. Its most noticeable feature is the crests above its eyes, probably used to attract mates and keep the sun out of its eyes. Allosaurus had 20-degree vision, meaning its vision overlapped in a small area, so if prey left that field, Allosaurus would struggle to track with depth perception. Allosaurus had a relatively basic brain structure similar to that of a crocodile. It had a large olfactory bulb but a small piriform cortex, meaning it had a strong sense of smell, but had trouble recognizing and processing advanced smells. Its ears were adapted for low-frequency noises, which indicates they communicated with such noises as grumbles. They had well-developed, long arms with 3 digits often having tendon avulsions, indicating Allosaurus likely used its arms in combat upon struggling prey such as Dryosaurus or Camptosaurus before they could run away, injuring their arms in the process. Allosaurus scavenged at possibly hunted weak, sickly, or juvenile sauropods such as Diplodocus, Pleurocoelus, Apatosaurus, and Camarasaurus. Allosaurus and Stegosaurus likely fought frequently throughout their lives, with Stegosaurus found to have Allosaurus bite marks on its plates. In contrast, an Allosaurus was found with a hole in its pelvis from a Stegosaurus's thagomizer. Ceratosaurus was another large theropod coexisting with Allosaurus, though it was smaller; the two are determined to have a fierce rivalry, with locations only consisting of one species of fossils as they held territory from the other. Of its species A. fragilis is type species and the most commonly found. A. europaeus is just like A. fragilis, but for specimens from Portugal. A. jimmadseni came 5 mya before A. fragilis and has a lighter build than it. Allosaurus is part of the group Allosauridae, of which it is the only member. Another species once part of the group called Saurophaganax was believed to be similar to Allosaurus but larger, although bones from a sauropod have been mixed in with it. Those Allosaurus bones have been assigned to A. anax, but I wish Saurophaganax was still a valid genus because the name means “lord of the lizard eaters” which is an awesome name. Allosaurus went extinct at the end of the Jurassic for unknown reasons, but likely due to climate change, the disappearance of prey like sauropods and competition from other carnivores like early carcharodontosaurs.