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Ltryptophan's avatar

Am I supposed to believe that tiny arms on dinosaurs was perfectly normal?

Asked by Ltryptophan (9100 points ) September 2nd, 2011

So, a giant meat eating dinosaur has itsy bitsy little arms. Lions don’t. Alligators do, but so are there back ones, and they are right against the ground!

Birds have long arms. I think this is a conspiracy to cover up that dinosaurs were doing something with those fancy little arms with the limp wrists.

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11 Answers

ragingloli's avatar

The Tyrannosaurus just did not use its arms, so they became vestigial, like humans’ ear muscles.

Nullo's avatar

@ragingloli * wiggles ears *

CWOTUS's avatar

I suspect that what happened during the evolution of T Rex (and other theropods) was that the hind legs developed, and the forelimbs developed “less” or “more slowly” than those hind legs, which were more valuable to the organism in developing a powerful gait (and lunge with the neck and jaws, if the animal really was a predator – there’s a lot of discussion among paleontologists about whether it was in fact a predator or scavenger). The forelimbs are not “vestigial”, but are actually quite well-developed and strong for their relatively smaller size. They only look “tiny” in relation to the size of the rest of the adult organism, which grew to about the size of a city bus. Viewed in that light, arms that are four feet long or so (and strong) aren’t “tiny”, they’re just not proportional to the size of the hind legs.

Cruiser's avatar

Tiny arms are sexy! ;)

digitalimpression's avatar

Our arms are shorter than our legs. Aren’t they?

gasman's avatar

Wikipedia has this to say about Tyrannosaurus’s arms:

…they are not vestigial but instead show large areas for muscle attachment, indicating considerable strength. This was recognized as early as 1906 by Osborn, who speculated that the forelimbs may have been used to grasp a mate during copulation.[58] It has also been suggested that the forelimbs were used to assist the animal in rising from a prone position.[53] Another possibility is that the forelimbs held struggling prey while it was dispatched by the tyrannosaur’s enormous jaws. This hypothesis may be supported by biomechanical analysis.

Keep in mind that for a creature to “build” large, strong limbs diverts limited resources otherwise invested into other parts of its body. T. rex & its small-armed cousins were successful species for millions of years until the K-T boundary catastrophe. Evidently its huge legs, tail, and jaws alone were a winning combination – and as the article points out, the arms were not totally pathetic, either.

Nullo's avatar

@digitalimpression IIRC the distance from the tip of one middle finger to the other is roughly equal to our height.

digitalimpression's avatar

@Nullo Yes, but just one arm is shorter than just one leg… yes? unless you’re strangely proportioned that is.

sophiesword's avatar

well It does make sense because many of the carnivorous dinosaurs had immense jaw power(obviously) and their muscular hind legs allowed them to run fast so they had little use for their arms.

But I guess you do make an interesting point however you cant ignore fossils of these ancient giants.

hiphiphopflipflapflop's avatar

When birds aren’t flying (or swimming in the case of penguins) they appear to manage quite well (naturally!), walking around on two legs and using their beak to pick up and manipulate objects and generally keeping their wings folded.

ucme's avatar

They were shit at volleyball.

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