Tyrannosaurus Forelimbs Revisited

Earlier in the week, I posted some theories regarding the function of T. rex’s diminutive arms. I just thought I would add some recent research before I closed the topic:

Matt Smith (Museum of the Rockies) and Ken Carpenter (Denver Museum of Natural History) began examining the wrist, hand and finger bones of the T. rex forelimb and used wax to hold the bone joints together. This led them to figure out that the forelimb's two claws have an unusual feature: unlike the opposable human thumb and forefinger combo, which can grasp objects, the two dinosaur claws face away from each other like the barbs of a fishing hook.

What does this mean? Perhaps these claws embedded themselves into the prey’s flesh and immobilized it while T. rex used his jaws to finish the job. .

Matt Smith says, "People had been looking at [forelimb] function based on proportionate size. I don't think that's appropriate."

What were T. rex’s tiny little arms for anyway?

American palaeontologist Henry Osborn first described T. rex but initially expressed doubts that the diminutive arms he found belonged to this enormous animal. After investigating further and finding it to be true, he considered their purpose and advanced the first theory in 1906: that they were used as ‘graspers’ or stabilizers during copulation.

But this was only the start of a debate that still rages. In 1970 British palaeontologist Barney Newman suggested that the small arms braced the beast's body as it stood up.
Another, contrasting theory suggested that the small limbs are vestigials (degenerated organs that have lost their use).

To add to the confusion it seems that the muscular of the T. rex was very well defined and though the arms were disproportional to the animal's body, they were still very strong. So some people consider that the most useful function of the limbs was to be used as meat hooks while the animal fed. This theory is supported by the beautifully sharp claws on T. rex’s two fingers.

In contrast, Greg Erickson has recently commented on a biomechanical analyses of a new specimen. The aim of this study was to try and understand the physical capacities of T. rex's diminutive structures. Erickson has concluded that the elbow could not be extended beyond 90° and though the arms were very strong (they could lift about 180 kg or 400lbs) they had a very limited side-to-side and up-and-down motion.

It is also known that T. rex's arms were often broken (and mended) during its life, suggesting that the arms were poorly suited for their function that these animals could go without using their arms for extended periods of time.

I read an interesting theory a while back that suggested the arms were most useful in juveniles, as a counterbalance to the young dinsaurs fast quickly. The suggestion was made that the arms were proportionally longer in childhood compared to adulthood. However, as far as I know this theory did not gain popularity.

The truth is that no one knows the answer. Scientific inquiry into this issue has been going on for a century and it doesn’t seem likely that the mystery will be solved soon. If you have any other ideas, please let me know!

Ancient proteins link T. rex to chickens

Well I’m sure everybody has seen this sensationalist headline in the last week, instead of tackling the controversy myself, I’ve decided to list a few posts by bloggers who have already posted on the topic:

PZ Meyers of Pharyngula posts Stone soup; or, extracting protein fragments from T. rex bones

Brian Switek of Laelaps in his post, And the T. rex goes… cock-a-doodle-do?

Mike Ryan of Palaeoblog posts T. rex Protein Sequenced

And the original article:
Analyses of soft tissue from Tyrannosaurus rex suggest the presence of protein. 2007. Science 316: 277 - 280

High Stakes Custody Battle for Fossil Dinosaur Continues

Custody battles for fossils can bring big money these days so it comes as no surprise that it was announced today that a 2 ½ year custody battle for the ownership of Tinker, a juvenile Tyrannosaurus rex will continue. A federal court of appeal ruled that a the lease formed between fossil hunters, who dug up the 65 million-year-old fossil and the County of Harding County, South Dakota was valid. This reverses a ruling made last year that deemed the lease void because it didn't follow a state law that requires leases exceeding 120 days and $500 USD to go before a public hearing.

Tinker is currently interned in Pennsylvania. An offer of $8.5 million USD has been made for the extraordinary fossil skeleton. In 1992, South Dakota saw another a custody battle for a dinosaur skeleton: Sue, a beautifully preserved, 13m (42ft) long T. rex specimen was at the center. Claims to Sue were made by a local rancher, a team of fossil hunters, a Sioux Indian tribe and the United States Government. It ended seven years later by awarding the dinosaur to the rancher on whose land the find was made. He then auctioned her off at Sotheby's, the winning bid went to Chicago's Field Museum with corporate sponsorship from McDonald’s and Walt Disney to the tune of $8.4 million. To date, it has been the most expensive fossil ever sold, I wonder if Tinker will break the record?

Creationist Museum Signs

Earlier today I wrote post about how Tyrannosaurus rex ate coconuts and how all dinosaurs used to be herbivores, at least according to a new Creationist museum in Kentucky, USA. In response, a reader sent me some hilarious signs that would be well suited to the museum:

Environmental message
“Another flood will make fossil fuels a renewable energy source”

Cafeteria menu
“Fish Sticks are organic and are not your relatives”

“Today’s special: Buy a spaghetti monster and get a free drink”

Museum Shop
“The Danny Dinosaur Adventure Ride is closed today. Please visit the Adam and Eve organic fruit and pet store”

T. rex ate coconuts

A new museum in Petersburg, Kentucky greets visitors with a 20ft tall tumbling waterfall and at its base, mannequins of frolicking children play amongst dinosaurs. The Creation Museum, which cost $25 million to build, is home to many unusual sites: a diorama of ancient people overshadowed by a towering T. rex, Adam and Eve swimming in a river with giant reptiles, and even a scale model of Noah's Ark. It seems Noah solved the problem of fitting dinosaurs into his vessel by only taking baby dinosaurs. Indeed, the ark has a detailed display of many animals happily boarding the boat: dinosaurs cavort with giraffes, penguins, hippos, and bears.

Museum guides tell visitors that before Adam and Eve were expelled from paradise all of the dinosaurs were peaceful plant-eaters. In Genesis 1:30 God gives ‘green herb’ to every creature to eat and so there were no predators. When a curious museum visitor asks, why exactly T. rex had six-inch long serrated teeth, the guides go on to explain that T. rex used his big teeth to open coconuts. Apparently it was only after Adam and Eve sinned and were cast out of paradise that the dinosaurs started to eat flesh.

My opinion: I think the people who built this museum are smoking a bit too much ‘green herb’.

In the News...

Big news in palaeontology this week, Graeme Lloyd posts on yet another gliding reptile in This Life is a Fiction, Matt Celeskey discusses Oryctodromeus, a burrowing dinosaur in his blog, The Hairy Museum of Natural History and Michael Ryan declares that T. rex Wins By A Nose in Palaeoblog.

Friday's Mystery Fossil Revealed

Congratulations to Mambo Bob for his response. Friday's Mystery Fossil was indeed a theropod and specifically a Tyrannosaurus but not Sue of the Chicago Field Museum. Rather, the picture is of a specimen at Palais de la découverte in Paris. Also, points Malacoda for his imaginative guess (an obvious asset in palaeontology:)

The image may be familiar to some as it was featured in my January posting, CSI: Garfield County.

Image copyright ©2005 David Monniaux.