Why did Tyrannosaurus Rex have such small arms?

Question

What purpose could there be for limbs as small as that?

Answer 1

Because it was most likely a scavenger and not a predator. It did not need large arms to hold its prey, because it only ate animals that were already dead.

This theory is relatively new and still hotly debated, but it explains quite a few things.

from: http://sfgate.com/cgi-bin/article.cgi?file=/c/a/2001/02/05/MN133208.DTL&type=science

Sight and smell

In support of the scavenger theory, scientists cite T. rex's relatively small eyes as evidence that it could not have been an effective hunter. Rather, its acute sense of smell - provided by a large olfactory lobe similar to a vulture's - would have enabled it to detect carrion from far away.

Teeth

Scavenger theorists contend that the rounded shape of the teeth - combined with its powerful jaws - was designed for crushing the bones of carcasses and getting to the meat in less accessible places. Other dinosaurs, like Velociraptor, had flat, knife-like teeth more suited to predatory attacks, they say.

Arms

Scavenger theorists argue that T. rex's short, vestigial arms were too weak to aid in capturing and holding prey. Others believe that they were not necessarily used in predatory attacks and say that many other predators - like snakes, sharks, crocodiles and many birds - either do not have or do not use forelimbs to attack their prey.

Legs

Scientists differ on whether T. rex's giant legs were built to endure over long distances - necessary for scavengers to maximize the area of potential food sources - or to provide quick bursts of speed to chase down prey. .

And on that note "...according to James Farlow, a palaeontologist at Indiana-Purdue University in Fort Wayne, Indiana, "If T. rex had been moving fast and tripped, it would have died." [53] If it tripped and fell while running, a tumbling tyrannosaur's torso would have slammed into the ground at a deceleration of 6g (six times the acceleration due to gravity, or about 60 m/s²)."

from http://en.wikipedia.org/wiki/Tyrannosaurus

Answer 2

Tyrannosaurus Rex Arms

Answer 3

This Site Might Help You.

RE:
Why did Tyrannosaurus Rex have such small arms?
What purpose could there be for limbs as small as that?

Answer 4

There are many examples of animals living today that have 'vestigial' parts to their bodies. This means a body part that has, for example, diminished in size over thousands or millions of years of evolution because it has become redundant. An example would be the slow worm, a lizard that looks like a snake because it has no legs but which on close examination can be seen to have tiny nodes where its legs once were; these legs became redundant when the animal, for whatever reason, came to find itself capable of moving in the manner of a snake. The process, incidentally, can work both ways i.e. a slow worm that found itself needing its legs again to survive would evolve them again or a species of snake that might never have had legs could evolve them.

The tyranosaurus' tiny forelegs were that way in the fossils we have found of them because that was the stage of evolution that they were at when they were wiped out. They clearly were surviving and breeding without longer forelimbs so having long forelimbs was not necessary to them; this means they must have been doing what they did (killing and eating other dinosaurs) in some manner that didn't use the forelimbs e.g. by waiting stealthily in shadows and then rushing out upon its prey upon its powerful hind legs (which were similar to those of an ostrich today) and catching the prey in its massive jaws. Would it need forelimbs to tear meat off the prey and put it into its mouth? Obviously not, since its forelegs were too short to reach; therefore it MUST have gotten its meat into its mouth some other way e.g. by standing on the meat, leaning forwards and biting into it, and then rising up to tear the meat from the carcass. Birds can be seen today tearing food morsels in this way.
So in short, there WAS no purpose for those short forelimbs of the tyranosaurus.

Answer 5

It evolved from animals such as lizards and reptiles like that but as it started to walk upright it had little use for them as all the dirty work was done with its huge teeth and there was never any weight on them so wasting proteins and goodnesses for growing on the arms would be pointless.

Answer 6

Just a guess because of balance. If the T-Rex has long arms it will look like a Gorilla with a tail.

Answer 7

Since they had such large teeth for killing, their short arms were not necessary.

Answer 8

We were all in a sales training session and were asked to think of a theory for the extinction of the dinosaurs and mine was that they all became gay, and my evidence was the arms of the T. Rex, useless for anything except flapping its wrists.

Answer 9

It couldn't reassemble an M16.

Answer 10

to push themselves up off of the ground after they'd had a little rest. I think they slept on their stomachs with their chins relatively flat on the ground and used their little arms to get up.