GREG HELGESON, MACALESTER COLLEGE

A nine-meter-tall carnivorous dinosaur probably wouldn't need much help establishing a ferocious reputation. But researchers writing in the journal Nature have discovered another trait of the species Majungatholus atopus that is sure to do just that. It seems that this dinosaur, which roamed Madagascar between 65 and 70 million years ago, was a cannibal.

Raymond Rogers of Macalester College and his colleagues analyzed 21 fossilized bones that were recovered from sites in Madagascar over a 10-year excavation period. The remains, which came from two Majungatholus individuals, have distinct markings that match the size and spacing of teeth in another Majungatholus skull (see image). In addition, smaller grooves on the bones correspond to the sharp serrations on the creature's teeth. "We have the smoking gun in the form of diagnostic tooth marks, and we can definitely rule out all of the other carnivores known to have been on the scene," Rogers explains.

Another dinosaur, Coelophysis bauri, had previously been accused of cannibalism based on interpretations of fossils that suggest the presence of a juvenile individual's remains in the stomach region of an adult Coelophysis. But that evidence needs to be reexamined, Rogers states, although it's still possible that that species, too, fed on its own. As for Mujungatholus, exactly why it devoured its own kind remains unclear. Says Rogers: "We don't know whether Majungatholus killed both of the individuals in our sample, or opportunistically scavenged their remains."