page_title: Allosaurus
section_title: Feeding
hierarchical_section_title: Allosaurus / Feeding
caption_attribution_description: Allosaurus skull cast in front view at the Museum für Naturkunde, Berlin.
context_page_description: Allosaurus was a large theropod dinosaur from the Jurassic period, a predatory carnivore.
  Allosaurus averaged 8.5 metres in length, though some remains suggest it could reach over 12 meters. Its three-fingered forelimbs were smaller than its large hind legs, and the body was balanced by a long, heavy tail. It weighed 2/3 tons.
  It is the most common large predator found in the Morrison Formation of North America. This formation was laid down 155 to 145 million years ago, in the Jurassic.
  Allosaurus was at the top of the food chain. It probably preyed on large herbivorous dinosaurs and perhaps even other predators. Potential prey included ornithopods, stegosaurs, and sauropods.
  Some paleontologists think Allosaurus had cooperative behavior, and hunted in packs. Others believe they may have been aggressive toward each other.
  Groups have been found together in the fossil record. This might be evidence of pack behavior, or just the result of lone individuals feeding on the same carcass.
  Remains of many individuals have been found, including some which are almost complete. Over sixty-nine individuals from one species have been found.
context_section_description: Sauropods, live or dead, seem to be likely candidates as prey. Sauropod bones with holes fitting allosaur teeth, and the presence of shed allosaur teeth with sauropod bones have been found.
  There is dramatic evidence for allosaur attacks on Stegosaurus. An Allosaurus tail vertebra has been found with a partially healed puncture which fits a Stegosaurus tail spike. Also, there is a Stegosaurus neck plate with a U-shaped wound that correlates well with an Allosaurus snout.
  Allosaurus was probably not a predator of fully grown sauropods, unless it hunted in packs. It had a modestly sized skull and relatively small teeth, and was greatly outweighed by adult sauropods. Another possibility is that it preferred to hunt juveniles instead of fully grown adults.
  Researchers have made other suggestions. Robert T. Bakker compared the short teeth to serrations on a saw. This saw-like cutting edge runs the length of the upper jaw, and could have been driven into prey. This type of jaw would permit slashing attacks against much larger prey, with the goal of weakening the victim.
  Another study showed the skull was very strong but had a relatively small bite force. The authors suggested that Allosaurus used its skull like a hatchet against prey, attacking open-mouthed, slashing flesh with its teeth, and tearing it away without splintering bones.
  They suggested that different strategies could be used against different prey. The skull was light enough to allow attacks on smaller and more agile ornithopods, but strong enough for high-impact ambush attacks against larger prey like stegosaurs and sauropods.
  Their ideas were challenged by other researchers, who found no modern examples of a hatchet attack. They thought it more likely that the skull was strong to absorb stresses from struggling prey.
  The original authors noted that Allosaurus itself has no modern equivalent, so the absence of a modern 'hatchet attacker' was not significant. They thought the tooth row was well-suited to such an attack, and that articulations (joints) in the skull helped to lessen stress.
  Another possibility for handling large prey is that theropods like Allosaurus were 'flesh grazers' which could take bites of flesh out of living sauropods, sufficient to sustain the predator so it did not need to kill the prey outright. This strategy might have allowed the prey to recover and be fed upon again later.
  Another idea is that ornithopods, the most common available prey, could be subdued by Allosaurus grasping the prey with their forelimbs, and then making bites on the throat to crush the trachea. The forelimbs were strong and capable of restraining prey, and the articulation of the claws suggests that they could have been used to hook things.
  The shape of the Allosaurus skull limited binocular vision to 20° of width, slightly less than that of modern crocodilians. As with crocodiles, this may have been enough to judge prey distance and time attacks. The similar width of their field of view suggests that allosaurs, like modern crocodiles, were ambush hunters.
  Finally, the top speed of Allosaurus has been estimated at 30 to 55 kilometers per hour (19 to 34 miles per hour).
caption: Allosaurus skull cast in front view at the Museum für Naturkunde, Berlin
exif: {"Image Orientation": "Horizontal (normal)", "Image XResolution": "96", "Image YResolution": "96", "Image ResolutionUnit": "Pixels/Inch", "Image Software": "Adobe Photoshop CS3 Windows", "Image DateTime": "2016:08:28 20:51:19", "Image ExifOffset": "164", "Thumbnail Compression": "JPEG (old-style)", "Thumbnail XResolution": "72", "Thumbnail YResolution": "72", "Thumbnail ResolutionUnit": "Pixels/Inch", "Thumbnail JPEGInterchangeFormat": "302", "Thumbnail JPEGInterchangeFormatLength": "3987", "EXIF ColorSpace": "sRGB", "EXIF ExifImageWidth": "810", "EXIF ExifImageLength": "1354"}