The formidableTyrannosaurus rexlikely had nothing to fear—except possibly its own kind, a new study suggests.
PaleontologistNick Longrichof Yale University was examining dinosaur bones found inMontanawhen he noticed large gouges in bones that had yet to be indentifiied.
The gouges had to have been made by a large carnivore, he said, and when the mystery fossils were deposited 65 million years ago,T. rexwas the only North American carnivore large and toothy enough to make such marks.
But the seemingly routine find took a macabre turn when Longrich discovered one of thebitten bones belonged to aT. rex—making it apparent evidence of cannibalism.
This toe bone"has giant theropod bite marks, and the only one there {at that time} wasT. rex,"he said."There was really no other conclusion I could come to."(Related:"TinyT. rexAncestors Achieved World Domination.")
Further analysis in several fossil collections turned up three more similarly bittenT. rexbones.
Longrich and colleagues speculate the giant predators may have engaged in cannibalism with some regularity—but it's unknown whether the dinosaurs fought to the death or simply scavengedT. rexcorpses.
T. RexCannibalism Would Mirror Modern Reptiles
Many modern predators, including distant dinosaur relatives such askomodo dragonsandcrocodiles, are known for cannibalistic behavior—particularly of their young.
Although the practice hasn't been well documented among dinosaurs, scientists do thinkMajungatholus atopus,a 30-foot-long (9-meter-long) theropod,dined on its kin on the island of Madagascar 65 million years ago.
Hans-Dieter Sues, curator of vertebrate paleontology at the National Museum of Natural History in Washington, D.C., isn't at all surprised byT. rex's taste for its own flesh and blood.
"Meat-eaters of all kinds feed on dead animals, which, after all, are just meat lying around for the taking,"said Sues, who was not involved in the study.
"Even pigs, which are omnivores, eat other dead pigs. There is nothing remarkable about this at all."
EatenT. RexWas Dinosaur Leftovers?
There's one clue as to whether the eatenT. rexwas killed or scavenged, Longrich noted: The cannibalistic bite marks appear to have been made some time after death.
(See"'Mighty'T. rexMostly Picked Off Youngsters?")
"It's kind of like the turkey on the fifth day after Thanksgiving—you're trying to get the last bits of meat off it,"he said."For the toes to be of interest, the carcass must have been pretty much picked clean."
But that evidence alone doesn't meanT. rexwas simply a scavenger, added Longrich, whose study appears online October 15 in the journalPLoS ONE.
"I wouldn't rule out the possibility of some sort of intraspecies combat going on,"he said.
"We see that today when animals like bears and lions take each other out. They are competing with one another, and the best way to get rid of your competitor is to get rid of him for good."
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