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T. rex was a cannibal, scientists report

Oct. 15, 2010
Courtesy of Yale University
and World Science staff

The fearsome “k­ing” of the di­no­saurs, Ty­ran­no­saur­us rex, ate not just oth­er di­no­saurs but al­so its own kind, pa­le­on­tol­ogists say in a new re­port. 

Re­search­ers found bite marks made by oth­er T. rex on several of the gi­ant rep­tiles’ bones, ac­cord­ing to the study pub­lished on­line Oct. 15 in the jour­nal PLoS One.

Sci­en­tists say T. rex was the on­ly car­ni­vore in west­ern North Amer­i­ca 65 mil­lion years ago ca­pa­ble of mak­ing such large gouges, such as the ones seen here on a toe bone. (Cred­it: Nich­o­las Lon­grich/Yale Uni­ver­si­ty)

While search­ing through di­no­saur fos­sil col­lec­tions for anoth­er study on di­no­saur bones with mam­mal tooth marks, Yale Uni­vers­ity re­search­er Nick Lon­grich said he dis­cov­ered a T. rex bone with es­pe­cially large gouges.

“They’re the kind of marks that any big car­ni­vore could have made. But T. rex was the only big car­ni­vore in west­ern North Amer­i­ca 65 mil­lion years ago,” the place and ap­proxi­mate time from which the fos­sil came, he added.

Af­ter search­ing through a few doz­en T. rex bones from sev­er­al mu­se­um col­lec­tions, he said he found a to­tal of three foot bones, in­clud­ing two toes, and one arm bone that showed ev­i­dence of T. rex can­ni­bal­ism.

“It’s sur­pris­ing how fre­quent it ap­pears to have been,” he added.

The marks are def­i­nitely due to feed­ing, though it’s un­clear wheth­er scav­eng­ing or fight­ing led to them, Lon­grich said. He spec­u­lat­ed that if two T. rex fought to the death, the vic­tor might have made a meal out of his ad­ver­sary. “Mod­ern big car­ni­vores do this all the time,” he noted. “It’s a con­ven­ient way to take out the com­pe­ti­tion and get a bit of food at the same time.”

How­ev­er, the marks ap­pear to have been made some time af­ter death, Lon­grich said, mean­ing that if one di­no­saur killed anoth­er, it might have eat­en most of the meat off the more ac­ces­si­ble parts of the car­cass be­fore re­turn­ing to pick at the smaller foot and arm bones.

While only one oth­er di­no­saur spe­cies, Ma­jun­gath­o­lus, is known to have been a can­ni­bal, Lon­grich said the prac­tice was likely more com­mon than we think and that clos­er ex­amina­t­ion of fos­sils could turn up ev­i­dence imp­li­cat­ing still oth­er spe­cies.

While to­day’s large car­ni­vores of­ten hunt in packs, T. rex likely acted on their own, Lon­grich said. “These an­i­mals were some of the larg­est ter­res­tri­al car­ni­vores of all time, and the way they ap­proached eat­ing was fun­da­men­tally dif­fer­ent from mod­ern spe­cies,” he said. “There’s a big mys­tery around what and how they ate, and this re­search helps to un­cov­er one piece of the puz­zle.”

Lon­grich co-authored the re­port with col­leagues in­clud­ing pa­le­on­tol­ogist John Horner of Mon­tana Sta­te Uni­vers­ity.

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The “king” of the dinosaurs, Tyrannosaurus rex, didn’t just eat other dinosaurs but also its own kind, paleontologists say in a new report. Researchers found bite marks on the giants’ bones that were made by other T. rex, according to the study published online Oct. 15 in the journal PLoS One. While searching through dinosaur fossil collections for another study on dinosaur bones with mammal tooth marks, Yale University researcher Nick Longrich said he discovered a T. rex bone with especially large gouges. “They’re the kind of marks that any big carnivore could have made, but T. rex was the only big carnivore in western North America 65 million years ago,” the place and time period from which the fossil came, he said. After searching through a few dozen T. rex bones from several different museum fossil collections, he said he found a total of three foot bones, including two toes, and one arm bone that showed evidence of T. rex cannibalism. “It’s surprising how frequent it appears to have been,” he added. The marks are definitely the result of feeding, although scientists aren’t sure whether they are the result of scavengers or the end result of fighting, Longrich said. He speculated that if two T. rex fought to the death, the victor might have made a meal out of his adversary. “Modern big carnivores do this all the time,” he said. “It’s a convenient way to take out the competition and get a bit of food at the same time.” However, the marks appear to have been made some time after death, Longrich said, meaning that if one dinosaur killed another, it might have eaten most of the meat off the more accessible parts of the carcass before returning to pick at the smaller foot and arm bones. While only one other dinosaur species, Majungatholus, is known to have been a cannibal, Longrich said the practice was likely more common than we think and that closer examination of fossil bones could turn up more evidence that other species also preyed on one another. While today’s large carnivores often hunt together in packs, T. rex likely acted on their own, Longrich said. “These animals were some of the largest terrestrial carnivores of all time, and the way they approached eating was fundamentally different from modern species,” he said. “There’s a big mystery around what and how they ate, and this research helps to uncover one piece of the puzzle.” Longrich co-authored the report with colleagues including paleontologist John Horner of Montana State University.