bloodstream. The injuries were also found to be mostly healed. This healing may indicate that allosauroids had an intermediate metabolic rate, similar to non-avian reptiles, which means they require fewer nutrients in order to survive. A lower nutrient requirement means allosauroids do not need to undertake frequent hunts, which lowers their risk of sustaining traumatic injuries. Although the remains of other large theropods like tyrannosaurids bear evidence of fighting within their species and with other predators, the remains of allosauroids do not bear much evidence of injuries from theropod combat. Most notably, despite a good fossil record, allosauroid skulls lack the distinctive face-biting wounds that are common in tyrannosaurid skulls, leaving open the question of if allosauroids engaged in interspecies and intraspecies fighting. Allosauroid remains are also often found in groups, which implies social behavior. While there are alternative explanations for the groupings, like predator traps or habitat reduction due to drought, the frequency of finding allosauroid remains in groups supports the social animal theory. As social animals, allosauroids would share the burden of hunting, allowing injured members of the pack to recover faster. Paleobiogeography The paleobiogeographical history of allosauroids closely follows the order that Pangaea separated into the modern continents. By the Middle Jurassic period, tetanurans had spread to every continent and diverged into the allosauroids and the coelurosaurs. Allosauroids first appeared in the Middle Jurassic period and were the first giant taxa (weighing more than 2 tons) in theropod history. Along with members of the superfamily Megalosauroidea, allosauroids were the apex predators that occupied the Middle Jurassic to the early Late Cretaceous periods. Allosauroids have been found in North America, South America, Europe, Africa, and Asia. Specifically, a world-wide dispersal of carcharodontosaurids likely happened in the Early Cretaceous. It has been hypothesized that the dispersal involved Italy's Apulia region (the “heel” of the Italian peninsula), which was connected to Africa by a land bridge during the Early Cretaceous period; various dinosaur footprints found in Apulia support this theory. Allosauroids were present in both the northern and southern continents during the Jurassic and Early Cretaceous, but they were later displaced by the tyrannosauroids in North America and Asia during the Late Cretaceous. This is likely due to regional extinction events, which, along with increased species isolation through the severing of land connections between the continents, differentiated many dinosaurs in the Late Cretaceous. References Further reading Holtz, T. R., Jr.