The 3rd metacarpal of *T. rex*

[David Marjanovic <david.marjanovic@gmx.at>]

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From: "Mark Temple" <glitterboy2098@yahoo.com>
To: <DinosaurMailingList-KilledThreads@yahoogroups.com>
Sent: Friday, October 26, 2007 2:03 AM
Subject: [DinosaurMailingList-KilledThreads] well, this changes things

http://dsc.discovery.com/news/2007/10/17/tyrannosaurus-dinosaur.html?category=dinosaurs&guid=20071017093030

T. Rex's Missing 3rd Finger Found

[No, not the finger. Just the metacarpal, which apparently didn't end in a 
joint.]

Three-Fingered Beast 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 [sic?] 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.

"It's unquestionably the metacarpal," Quinlan told Discovery News. No
previous T. rex remains have ever been found with a third metacarpal,
despite the fact that the other bones suggested its presence. "There
is a notch in the side of the second metacarpal that was just begging
to have something fit into it."

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.

"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
[to think?] 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.

[I doubt the trend thing.]