Jurassic dinosaur Allosaurus may have been a cannibal

Examining the bones of Allosaurus, researchers find bite marks suggesting scavenging behavior and, possibly, cannibalism.

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The circle of prehistoric life.

Brian Engh

Dinosaur cannibalism is not just the most metal band name -- it's also a potential reality of the Jurassic age. Some of the most fearsome carnivorous dinosaurs of the Late Jurassic may have resorted to eating their own species, according to a new study examining bite marks on a trove of fossils unearthed in the US midwest.

The paper, published in the open access journal PLoS One on Wednesday, details a haul of fossils discovered in the Mygatt-Moore Quarry in Colorado and describes the unusually high proportion of bite marks found on the bones. The quarry contains a range of dinosaurs fossils from the late Jurassic, dating back to around 150 million years ago.

Studying over 2,300 bones, a team of paleontologists discovered nearly 29% contained bite marks from theropod dinosaurs, the group of mammoth carnivores which counts T. rex, Spinosaurus and Allosaurus among its ranks. Measuring the bite marks on the fossils, the team concludes at least two large theropods found at the site -- Allosaurus and Ceratosaurus -- as well as an even bigger carnivore not previously discovered at Mygatt-Moore, were feeding on carcasses left to rot in the prehistoric world.

The quarry is believed to preserve specimens from an ancient wetlands ecosystem, where carcasses were unlikely to disappear into the mud quickly. This gave huge predators a chance to scavenge meat from bone. The team found many of the bite marks on herbivore bones were located on places where the meat had high nutritional value, which makes sense for huge predators. 

However, those found on theropod bones were located on regions that provided less nutritional value -- suggesting the mammoth beasts weren't trying to hunt each other, but taking advantage of remains. Even more intriguing, the team believes they have discovered evidence of Allosaurus bite marks on Allosaurus bones. 

That would make it a Jurassic cannibal -- and the first evidence of cannibalism in Allosaurus.

"Big theropods like Allosaurus probably weren't particularly picky eaters, especially if their environments were already strapped for resources," said Stephanie Drumheller, a paleontologist at the University of Tennessee, Knoxville, in a press release. "Scavenging and even cannibalism were definitely on the table."    

That's an important discovery in the dino-world because, as the authors note, "direct evidence for it in the fossil record is extremely rare." 

The team point out there could be other reasons for the bite marks that don't relate to scavenging or cannibalism, too. For instance, these creatures may have competed with each other for food and thus got into a few dinosaur bar fights. Some modern-day crocodilians fight each other, leaving huge gashes and marks in the head, tail and limbs or opponents. However, the team says some of the bite marks are in locations that could only "reasonably be reached" after death or dismemberment.

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