New fossil evidence suggests a distant cousin of the Tyrannosaurus rex that roamed the plains of Madagascar millions of years ago regularly dined on its own kind to survive during hard times.
The discovery is the strongest evidence that some carnivorous dinosaurs were cannibals. Dinosaur experts say it sheds light on the hardships predators faced in the late Cretaceous period when dinosaurs vanished, possibly as a result of asteroid impacts, widespread climate change and disease.
"This is the first strong, convincing evidence of cannibalism within theropod dinosaurs," said Thomas Holtz, a paleontologist at the University of Maryland who was not part of the study.
Scientists working in Madagascar uncovered evidence of cannibalism in fossilized bones of Majungatholus atopus, a toothy beast the size of a small school bus that was the top hunter 70-million years ago on the island off east Africa.
The research appears in the current issue of the journal Nature.
Majungatholus is a distant relative of T. rex, the fierce hunter that ruled what is now North America. Scientists have speculated that T. rex was a scavenger and may have eaten other T. rexes killed in fights, but the evidence is not conclusive.
During the late Cretaceous, Madagascar was semiarid and subject to severe climate swings that led to dramatic fluctuations in essential resources. Fossil evidence showed dinosaurs and other creatures were victims of massive die-offs.
When food and water were scarce, scientists believe Majungatholus fed on the remains of other dinosaurs like titanosaurs -- gigantic, long-necked plant-eaters -- and even scavenged the carcasses of its own dead.
"It appears as though Majungatholus atopus exploited all available resources during stressful episodes, even if it meant dining on members of its own species," said Raymond Rogers, a geologist at Macalester College in St. Paul, Minn., and lead author of the study.
The reasons behind Majungatholus' cannibalism appear to be basic. Researchers examining 21 bones from two nearly full-grown specimens taken from separate quarries on the island found evidence of intensive feeding in the backbone area.
Rogers said sets of parallel tooth marks on the spine and ribs of the specimens matched the size and spacing of Majungatholus' blade-like teeth. The specimens do not show whether the dinosaur actually hunted down the other Majungatholus as prey or scavenged their carcasses.
Researchers ruled out the only other known meat-eating dinosaur in the area -- Masiakasaurus knopfleri -- because its teeth were too small. They also discounted carnivores like crocodiles that have blunt, irregular teeth.