Why did T-Rex have such teeny arms?

[electronbee]

Augh... edit did not take...

Any ways, there is a WikiPedia section for the arms. They are in fact very limited in their capability but I also think the neck can be folded over and down so the mouth and arms could meet.

As for the OP question... I think they were small as they did not need to be any bigger. The legs are well developed as are the jaws. There was a lot of muscle attacked to these two which dictates that how it got it's prey: a high-speed attack with a grappling bite to the body of the prey. The arms were probably folded-in out of harms-way. Those short, powerful, jaws probably crushed the prey to death. Once the prey was dead, the arms presumably held the carcass in place either on the ground or maybe a smaller chunk close to the chest while T-rex ripped pieces from it.

[Sr Siete]

Originally Posted by Colibri

It would have been impossible for Spinosaurus to have "run four-legged"; the arms are much too small for that, and are not articulated in such a way to make quadrupedal locomotion feasible for any distance. T. rex was not just "pretty much" bipedal; it was obligately bipedal.

T. rex's arms are proportionally smaller than those of most other theropods, making the question of why they were like that of some interest. Just saying that all theropods had small arms doesn't contribute anything to the discussion.

True enough. Still, the small arms of a Spinosaurus could be used to crouch or rest using them, much like an ape does.

And I honestly don't see a particularly unusual difference in proportional size between the Rex and other large theropods such as the Gigantosaurus. Pointing out what looks to me like a flawed premise is a fairly good contribution to the discussion, I think.

[BigT]

T-Rex was almost horizontal when he ran, right? So the arms would have further reach than you'd think if he were always upright.

[AaronX]

Could they be used to protect the neck and chest from fighting prey?

[Corcaigh]

Originally Posted by Scumpup

They were used to wave threateningly.

yes, because let's face it, his arms were the scariest part of his anatomy

Originally Posted by panache45

For giving two snaps and a hey.

Or applauding the play at golf matches!

[Elendil's Heir]

I always thought it was to hold its cigarettes: http://1.bp.blogspot.com/_WQbgYtjne5...00/extinct.jpg

[Snickers]

Could we look to the kangaroo for an answer to this, or is that just ridiculous? I mean, the 'roo has relatively small upper limbs combined with a long, powerful tail and larger powerful legs. Roos commonly use their upper limbs for balancing while grazing in a quadrupedal way, and also during high-speed locomotion.

(I'm not saying that T-Rexes bounced their way along, mind. But perhaps their upper limbs were just long enough to use in a similar way.)

Not sure whether 'roo upper limbs are proportionally longer than T-Rexes, though.

[Scumpup]

Originally Posted by Corcaigh

yes, because let's face it, his arms were the scariest part of his anatomy

Would you be willing to arm wrestle with a T-Rex? I didn't think so.

[TriPolar]

T. Rex forelimbs seem to be proportionally smaller than kangaroos, and unable to reach the ground unless the beast is lying on it's belly. The are also very small in proportion to all the every other part of their body. The hands also have an unusual two claw form. Fossil bones indicate the arms were heavy and well muscled, so not useless if they could reach something.

But the mystery is also one of expectations. Someone examining modern mammal fossils might wonder why humans had such a small tail. As mentioned previously in the thread, a variety of dinosaurs had proportionally small forelimbs, something that would be expected in animals with T form bipedalism. Somewhere along the line, T. Rex ancestors may have simply developed progressively larger legs, heads, and tails, while never developing large forelimbs because there was no benefit from them. And possibly there was a benefit from having them proportionally smaller, but we may never find enough evidence to determine what that benefit was.

[Shakester]

Originally Posted by Snickers

Not sure whether 'roo upper limbs are proportionally longer than T-Rexes, though.

They are.

[Exapno Mapcase]

Originally Posted by Scumpup

Would you be willing to arm wrestle with a T-Rex? I didn't think so.

Already been done.

Here comes the science: Could a Human Beat a T. Rex In Arm Wrestling?

[Scumpup]

You're forgetting something important: T-Rex cheats at arm wrestling and gay chicken.

[Rhythmdvl]

Originally Posted by Polycarp

This is what T. rex was faced with, and he couldn't bang a gong for help.

Originally Posted by TriPolar

A counter-position to Chronos' assertion that they used the short arms to get it on.

Originally Posted by Ludovic

I see even other species have problems with all their young dudes.

Now that's a series of possibly under-appreciated brilliance.

T. Rex
Bang a Gong (Get It On), a song by T. Rex
Mott the Hoople sang All the Young Dudes which references T. Rex in their lyrics "Man, I needed TV when I got T. Rex"

Fucking brilliant.

I'd link to the songs on Youtube, but I don't have sound here and can't tell if I'd be linking to a dead video. But definitely worth checking out.

[Ksnook]

Right, then. I'm off to The Hundred Acre Wood to ask Kanga, who always has the answers.

[C K Dexter Haven]

Originally Posted by njtt

When I Googled it, the plural was Reges.

If we are considering it to be a word fully adopted into English, rather than Latin, then surely it would be rexes.

I prefer T's-Rex, sort of like mothers-in-law.

[Elendil's Heir]

Originally Posted by C K Dexter Haven

I prefer T's-Rex, sort of like mothers-in-law.

Or attorneys general.

[mlees]

If a T-rex had a grip on prey with it's mouth, could the arms be used to inflict further damage?

Like a cat can rake/claw with it's legs while holding it's prey with a bite.

I grant that the damage comparison between a cat's bit and it's legs make them a bunch more equal than a T-rex bite compared to a T-rex arm gouge, but still...

[Corcaigh]

Originally Posted by Scumpup

Would you be willing to arm wrestle with a T-Rex? I didn't think so.

Well not me personally, no. I have very weak wrists being a gurl an all!

Originally Posted by mlees

If a T-rex had a grip on prey with it's mouth, could the arms be used to inflict further damage?

Or hold live prey still while he chowed down...?

[drachillix]

[quote=Son of a Rich;15070621*what's the plural of T-rex?[/quote]

RUN!!!

[Lemur866]

Originally Posted by drachillix

RUN!!!

I don't have to run faster than a Tyrannosaur, drachillix. I just have to run faster than you.

[Darwin's Finch]

It could be that T. rex's arms were of more use to juveniles, and of little to no use for adults. Tyrannosaur body proportions changed as they aged, as happens with many animals, and it is suspected that juveniles were, among other traits, more athletic than were the adults.

For example, the tyrannosaurus specimen nicknamed "Jane" is thought to be a juvenile. Note that the arms, while still small, aren't quite as comparatively tiny as they are in adult rexes.

This could explain why the forelimbs appear so useless in adults, but were nevertheless retained.

[Lukeinva]

Perhaps to help care for baby Rex? Such as digging out a nest, etc.

[Memoe]

Could they have actually been Caresses, some birds are born with claws on their 1st and 2nd digits today. If they were located farther out on a wing it would make sense as to why the bones are usually found several feet from the actual body. It would explain the shape of the shoulder blade and many other discrepancies in the archeological records.

[Autolycus]

Well duh, how else are they going to pilot the F-14s?

[Evil Captor]

Actually you guys came VERY CLOSE with your theory that they used their tiny claws to pick their teeth. Tyrannosaurs actually used their tiny forelimbs to pick OTHER dinosaurs' teeth. They were the cleaner wrasses of the Jurassic ecosystem, according to science1. They would stand in a clearing and all the other dinosaurs would line up to have their teeth cleaned. Scientists theorize2 that the large size and teeth of tyrannosaurs was to terrify other dinosaurs into holding still while their teeth were being cleaned.

1. Bruckner and Feldspar, "Look At The Cool Theory We Just Made Up," Journal of Irreproducible Results, 2006.
2. Made you look!

[dauerbach]

Then you have vestigial organs that are selected against and persist without known function. The human appendix has no know function, and until recently those with appendicitis had a great chance of dying, and this often occurred before the age of reproduction.

[Colibri]

Originally Posted by dauerbach

Then you have vestigial organs that are selected against and persist without known function. The human appendix has no know function, and until recently those with appendicitis had a great chance of dying, and this often occurred before the age of reproduction.

Actually, recent research has found that the appendix does have a function in the immune system. It may also serve as a reservoir for beneficial intestinal bacteria.

[maconlists]

All of the above noted functions for the forelimbs would be better if the forelimbs were bigger. The issue of balance seems unlikely compared to the possibility of having a slightly longer or thicker tail. It has been noted that the trend started in T. Rex smaller feathered ancestral species. Isn't it more likely that they didn't evolve smaller arms but actually evolved smaller WINGS (as now seen on flightless birds). I'm sure an ostrich would love to have functional arms if given the choice but you can't go back.

[johnpost]

zombie or no

it was a sausage eater.

[Elmer J. Fudd]

Originally Posted by njtt

When I Googled it, the plural was Reges.

If we are considering it to be a word fully adopted into English, rather than Latin, then surely it would be rexes.

Not tyrannosauri rex?

[Polycarp]

T-Rexes used their forelimbs to go Bolan.

[Darwin's Finch]

Originally Posted by maconlists

Isn't it more likely that they didn't evolve smaller arms but actually evolved smaller WINGS (as now seen on flightless birds).

No.

[Earl Snake-Hips Tucker]

Originally Posted by Elmer J. Fudd

Not tyrannosauri rex?

Not in English, at least according to the editors at Merriam-Webster. "Tyrannosauruses" or "T. rexes."

[auntlohimein]

- Bearded dragons [small lizards from australia], the female 'waves' one of her upper legs [arms i guess] to show submission to males! SO-

[auntlohimein]

to add- - pythons and boa's have vestigial hips/legs and, external "claws", i have many times, watched males "stimulating," scratching females they are trying to mate with, its sometimes hard to believe how far a range of motion these little claws move! Its generally though, but i could be wrong, that the males have larger spurs. So could T-rex "caress" his mates neck?

[Grendel's Father]

Originally Posted by Darwin's Finch

No.

Why not? It's now known that wings go back at least as far in the dino family tree as ornithomimids, which are only one or two branch up from tyrannosaurs.

http://skeletaldrawing.blogspot.com/...sas-adult.html

If the arms of large tyrannosaurids bore display feathers of some kind, this could partially explain the paradoxical small size plus heavy musculature (perhaps employed in some kind of flapping display?).

[Bosda Di'Chi of Tricor]

Originally Posted by tdn

They were used to play the ukulele.

The ukulele?
THE UKULELE? REALLY?!?


Everybody knows T-Rex played the Bassoon.

[Polycarp]

Originally Posted by tdn

They were used to play the ukulele.

Originally Posted by Bosda Di'Chi of Tricor

The ukulele?
THE UKULELE? REALLY?!?


Everybody knows T-Rex played the Bassoon.

You're both wrong!

[Darwin's Finch]

Originally Posted by Grendel's Father

Why not? It's now known that wings go back at least as far in the dino family tree as ornithomimids, which are only one or two branch up from tyrannosaurs.

http://skeletaldrawing.blogspot.com/...sas-adult.html

If the arms of large tyrannosaurids bore display feathers of some kind, this could partially explain the paradoxical small size plus heavy musculature (perhaps employed in some kind of flapping display?).

Couple of reasons:

1) The post to which I gave my terse response asked "isn't it more likely that they...actually evolved smaller WINGS?" That would require wings to already have been present among coelurosaurs, prior to Tyrannosauridae. Possible? Perhaps. But not "more likely", given our current knowledge of these groups.

2) Feathered forearms do not a wing make, any more than feathers alone make a bird. The time of feathers being a diagnostic character for birds is long gone. Similarly, the definition of "wing" ought to be further refined (note that even the cladogram in the linked Skeletal Drawings blog notes that actual wings don't appear until about the Paraves clade; Ornithomimids actually had a pennibrachium). Thus, if tyrannosaurs were found to have had feathered forelimbs, they could be also said to have a pennebrachium (contingent on the actual arrangement of these hypothetical feathers), but I wouldn't say they had actual wings.

[madsircool]

Originally Posted by Exapno Mapcase

Would you want to face a T. Rex? If the answer is no, then it doesn't really matter what its arms were like. They were just fine.

I would rather face a T Rex than a mammal predator for the reason that IIRC T Rex had no meylin sheathing on their neurons and their brains were far slower than ours. It would be easy to hide from one.

[Exapno Mapcase]

Originally Posted by madsircool

I would rather face a T Rex than a mammal predator for the reason that IIRC T Rex had no meylin sheathing on their neurons and their brains were far slower than ours. It would be easy to hide from one.

You mean like we don't have to worry about snakes and crocodiles and other reptiles, because they are so slow and stupid?

Or you could give me a cite that the T Rex had no meylin sheathing on its neurons.

[madsircool]

Originally Posted by Exapno Mapcase

You mean like we don't have to worry about snakes and crocodiles and other reptiles, because they are so slow and stupid?

Or you could give me a cite that the T Rex had no meylin sheathing on its neurons.

Investigate the work of Nicolai Bernstein

[TSBG]

That's not a cite, which is annoying, but in a generous mood I went so far as look at the Wiki for Bernstein. Nothing on T. Rex, or myelin. You need to do better.

[Exapno Mapcase]

Originally Posted by TSBG

That's not a cite, which is annoying, but in a generous mood I went so far as look at the Wiki for Bernstein. Nothing on T. Rex, or myelin. You need to do better.

If it's the same one who comes up first in Google, he died in 1966. And that means I can guarantee you that the sum total of his knowledge of myelin sheathing in T. Rex was exactly equal to that of madsircool.

[lieu]

Originally Posted by Palo Verde

Why did T-Rex have such teeny arms?

First rule of T-Rex... Don't talk about the T-Bone.

[monkeytail]

I think it's all about utility. I.e: Bigger doesn't necessarily mean better.
The reason T Rex arms were muscular were because the required them strong. The reason they were small were because (Speculative):
1. The center of gravity would've shifted forward if they hands were big.
2. They would've used their hands to claw and latch prey down rather than feed itself like most creatures do (I mean the nails were pretty big...)
3. (The really embarrassing bit) (Fe)male T Rexs liked small hands... Like how peacocks with large and colourful plumage are mostly chosen over less attractive and smaller ones.

In retrospection: They need big a jaw to crunch bones and tear flesh... big legs to run fast and big tail to balance... (Nature gave it to them)
But since they were bipeds and the hands weren't used to handle tools or do other energy demanding jobs... they probably became reduced over time... yet remaining strong enough to ensure that they could be used as a hunting devices for pinning, clawing or tearing...

[njtt]

This current thread might be relevant.

[msmith537]

Originally Posted by Chronos

One hypothesis I've heard is that they used them to hold onto each other for mating.

Probably why they were so cranky. It's hard to cuddle properly with such tiny arms.

[msmith537]

Originally Posted by madsircool

I would rather face a T Rex than a mammal predator for the reason that IIRC T Rex had no meylin sheathing on their neurons and their brains were far slower than ours. It would be easy to hide from one.

Did the T-Rex challenge it's prey to a game of Scrabble or something? Who cares how smart it was. I'd rather face a predator that's not as tall as a building.

[njtt]

Originally Posted by njtt

When I Googled it, the plural was Reges.

If we are considering it to be a word fully adopted into English, rather than Latin, then surely it would be rexes.

Originally Posted by C K Dexter Haven

I prefer T's-Rex, sort of like mothers-in-law.

Originally Posted by Elmer J. Fudd

Not tyrannosauri rex?

So you are thinking of Rex as functioning like an adjective, modifying tyrannosaurus?

Well, OK, but if (again) we are doing Latin, adjectives need to agree in number (and case) with the nouns they modify - so still Reges.