Planet Earth

Chomp Champ


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Was Tyrannosaurus rex nothing but a glorified carrion eater? Some paleontologists have proposed that T. rex’s gaping jaws and seven-inch-long teeth were too weak to contend with struggling prey and that this supposedly fearsome predator was merely a scavenger. But evolutionary morphologist Gregory Erickson, a graduate student at Berkeley, has shown that T. rex’s bite would have been strong enough to take down some very big game.

In 1991 a fossil hunter in Montana stumbled across a Triceratops pelvis scarred by dozens of scrapes, scratches, and punctures. It looked like a really big dog had gotten hold of it, says Erickson. A tyrannosaur apparently inflicted the scars--a cast of one of the punctures turned out to be identical to T. rex’s daggerlike upper teeth. But had the big carnivore killed or merely scavenged the Triceratops?

Erickson teamed up with some Stanford engineers to try to re- create what had happened to the Triceratops pelvis. Standing in for T. rex was a bronze-aluminum cast of one of its seven-inch front teeth, screwed onto a hydraulic press. The bronze-aluminum alloy, says Erickson, mimics the strength of tooth enamel. A cow’s pelvic bone, which is similar in its microstructure and strength to a Triceratops bone, became the unlucky prey.

Erickson slammed the metal tooth into the cow bone, measuring the force required to create a half-inch puncture identical to a hole in the Triceratops bone. The force of T. rex’s bite, Erickson calculates, was just over 3,000 pounds. That’s equivalent to a pickup truck’s weight behind each of this guy’s teeth, he says.

The most powerful set of jaws among living animals belongs to the American alligator, which can shut its trap with a force of 3,000 pounds, just like T. rex. (Humans weigh in at a measly 175 pounds.) But Erickson points out that the bite he re-created--he had the tooth move at a rate of about half an inch per second--was only a feeding bite, or a nip, not the deadly crush of a killing bite, which would have been directed at the head or neck of a grazing dinosaur like Triceratops, rather than the pelvis. T. rex could have bitten a lot harder and faster, but Erickson says he was purposely conservative in his experiment. There’s too much arm waving in paleontology already, he says. You don’t need to exaggerate Tyrannosaurus rex’s proportions in any manner. It’s an enormous, incredible beast.

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