Oct. 17, 2007 — It's bad enough to misplace a finger, much less have it lost for 65 million years. But after decades of searching, paleontologists at Montana's Hell Creek have found the missing third finger of one of Tyrannosaurus rex's undersized "hands."
The finger suggests that T. rex had a powerful wrist and its hands were probably able to hold onto chunks of flesh while the monster's gnarly jaws did all the killing.
The newfound bone is a right metacarpal, equivalent to one of the long bones in the palm of a human hand, explains T. rex investigator Elizibeth Quinlan of Fort Peck Paleontology, Inc., in Fort Peck, Montana. She plans to present the discovery on Oct. 28 at the annual meeting of the Geological Society of America in Denver.
The revised anatomy of the hand suggests there was a very strong tendon that attached to second metacarpal, giving the hand a pretty decent grip, she said. Still, the puny limbs were almost certainly not used by T. rex to grapple with prey or kill.
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"We were thinking that T. rex did use its upper appendages not so much in hunting but in feeding," said Quinlan. That means ripping off pieces of flesh from corpses and clutching the stuff to keep it from other hungry predators. "We don't think their table manners were very good."
"I would strongly support (the hand) being used for carrying a piece of meat away," said paleontologist Scott Hartman, science director of the Wyoming Dinosaur Center in Thermopolis. "There is a reason that carrying meat away would be useful."
One reason is that the T. rex head is already so large and heavy that adding the weight of a large slab of meat between its teeth would make it unable to tip back and stand up, Hartman said. Holding meat with the arms, which are lower, avoids that overloaded teeter-totter effect.
Another possibility is that the hands were parenting tools. They would have made it possible for a T. rex to carry yummy slabs of dino flesh to its carnivorous babies, Hartman said.
That said, the new finger bone is not going to cause much change to reconstructions of T. rex, says Hartman. Throughout the evolution of meat-eating dinosaurs there was a trend towards fewer fingers, with the earliest having five fingers and the T. rex having two. This newfound nubbin of a third finger was already on its way out, and did not stick out much, he said.
"In another 10 million years they would have lost (the third finger) completely," said Hartman. Unfortunately for them, however, the age of dinosaurs ended before that could happen.
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