and time attacks. The arms, compared with those of other theropods, were suited for both grasping prey at a distance or clutching it close, and the articulation of the claws suggests that they could have been used to hook things. Finally, the top speed of Allosaurus has been estimated at 30 to 55 kilometers per hour (19 to 34 miles per hour). A paper on the cranio-dental morphology of Allosaurus and how it worked has deemed the hatchet jaw attack unlikely, reinterpreting the unusually wide gape as an adaptation to allow Allosaurus to deliver a muscle-driven bite to large prey, with the weaker jaw muscles being a trade-off to allow for the widened gape. An alternate hypothesis by Pahl and Ruedas in 2021 suggested instead that Allosaurus subsisted primarily on carrion produced by sauropods. They proposed that sauropod carcasses were analogous to modern whale falls, in that they may have provided dense energy reservoirs to the entire ecosystem as the animals died naturally of starvation or exhaustion. However, the paper has been criticized for omitting direct fossil evidence of hunting behaviour in Allosaurus, overestimating scavengers' advantages over active predators, using unrealistic modelling assumptions about carcass availability, mortality risk, and energy expenditure, and for mis-representing previous works. Pahl and Ruedas suggested that the fossil evidence apparently demonstrating hunting interactions in Allosaurus are better explained by scavenging or by predation under extenuating environmental conditions, defended their modelling assumptions, and drew attention to a preference for scavenging among modern predators as well as the resistance to microbial infections imparted by a scavenging lifestyle. Social behavior It has been speculated since the 1970s that Allosaurus preyed on sauropods and other large dinosaurs by hunting in groups. Such a depiction is common in semitechnical and popular dinosaur literature. Robert T. Bakker has extended social behavior to parental care, and has interpreted shed allosaur teeth and chewed bones of large prey animals as evidence that adult allosaurs brought food to lairs for their young to eat until they were grown, and prevented other carnivores from scavenging on the food. However, there is actually little evidence of gregarious behavior in theropods, and social interactions with members of the same species would have included antagonistic encounters, as shown by injuries to gastralia and bite wounds to skulls (the pathologic lower jaw named Labrosaurus ferox is one such possible example). Such head-biting may have been a way to establish