Dinosaurs ate each other

Chewed bones convict ancient cannibal.

Majungatholus atopus measured more than 9 meters from nose to tail. Credit: © D. Vital

Dinosaurs roaming the plains of Madagascar more than 65 million years ago ate each other, gnawed fossil finds suggest. The bones and the tooth marks on them belong to members of the same species¹.

The remains are from Majungatholus atopus, a meat-eating, two-legged dinosaur that measured more than 9 metres from nose to tail. Ray Rogers from Macalester College in St Paul, Minnesota, and his colleagues analysed more than 20 gnarled bones, from two different individuals, found in an ancient riverbed. "Never have I seen material so chewed on," says Rogers.

The tooth marks on the bones perfectly match the teeth in a Majungatholus skull found in the same area, reports the team.

The bones have been mauled, much as coyote might chew a cow, explains Rogers. There are parallel sets of tooth marks, centimetres apart, across the ribs and backbones. The spacing and shape of the imprints do not match the dental profile of other animals that are known to have been alive at the time.

"This was the smoking gun," says Rogers, proving that this breed of dinosaur was a cannibal. "It gives us a wonderful view into the late-Cretaceous world of this animal."

These finds represent real evidence about how creatures actually behaved, agrees palaeontologist Eric Buffetaut of France's National Centre for Scientific Research in Paris. "A lot of what we hear and read about dinosaur behaviour is guesswork," he says.

Majungatholus did not dine exclusively on its own kind. Similar markings on a pelvic bone from a huge sauropod - a long-necked, pea-headed herbivore - suggest that the beast also ate other dinosaurs.

The bones were found in mass animal graveyards in Madagascar. Credit: © G. Helgeson

The relics were discovered by palaeontologists working on the Mahajanga Basin Project, a ten-year excavation of northwest Madagascar's spectacular bone beds. The bones were found in two mass animal graveyards, along with the remains of other dinosaurs, crocodilians, turtles, fish, frogs and birds.

Fossilised soil samples from the same region are red and oxidized, hinting that the area was arid, with food in short supply, says Rogers. The animals may have travelled to the river to find sustenance and died there. If so, Majungatholus may have been a scavenger desperately in need of a meal, rather than a predatory cannibal, Rogers speculates.

Cannabilism is still practised by several species today, including lions, komodo dragons, crocodiles and grasshopper mice. In contrast, evidence of cannibalism among dinosaurs is sparse.