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Cannibal dinosaurs

During the Late Cretaceous, a predatory dinosaur named Majungatholus atopus roamed the plains of what is now northwestern Madagascar. A study in the April 3 Nature now suggests that when times got tough, and food sources became scarce, the dinosaur turned to its own kind for a meal.

Majungatholus joins a short list of dinosaurs for which evidence points to cannibalism, says lead author Raymond Rogers, a geologist from Macalester College in St. Paul, Minn.

In this case, the evidence rests in tooth marks etched into Majungatholus bones excavated from the Maevarano Formation. Tiny, sharp denticles line the outer edge of Majungatholus teeth, much like serrations on a steak knife. The denticles would create closely spaced parallel lines as they dragged across bones, Rogers says. Two bones from Majungatholus — a rib and a V-shaped bone called a chevron — show extensive markings with precisely this pattern. In addition, the distances between the individual tooth marks closely match the distances between individual teeth in a fossilized Majungatholus jaw bone from the same formation.

Drawing by Demetrios Vital, University of Minnesota.

To document cannibalism, the authors had to rule out other suspects. The only other theropod known from the Maevarano Formation is Masiakasaurus knopfleri. Its jaws were too small to create the tooth patterns, says co-author David Krause, a paleontologist at the State University of New York in Stony Brook. Several crocodile-like species could have been culprits, but the spacing and height of their teeth were too irregular.

Majungatholus most likely did not hunt down its own kind — an endeavor that would probably take more energy than would be gained from eating the meat, Rogers says. Rather, Majungatholus probably scavenged on carcasses of fellow dinosaurs that were already dead.

A Majungatholus atopus rib shows tooth marks that could only have come from the teeth of another Majungatholus, according to the authors of the Nature study. Image by Raymond Rogers, Macalester Collegeogram.

Hans-Dieter Sues, a paleontologist at the Carnegie Museum of Natural History in Pittsburgh, says the study makes a compelling case for cannibalism. But, he adds, the find is not too surprising. "Cannibalism is common in nature. ... Almost any animal that scavenges food scavenges its own kind. Dead meat is dead meat."

Greg Peterson


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