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Why did T. rex and Other Dinosaurs Have Tiny Arms - Moth Light Media

What did T. rex use those arms for?

  • To aid in getting up

    Votes: 5 4.8%

  • To aid in SEX

    Votes: 43 41.0%

  • Slashing

    Votes: 1 1.0%

  • Holding onto prey for a better CHOMP

    Votes: 11 10.5%

  • Nothing, T.rex just didn't skip the arm days regardless

    Votes: 29 27.6%

  • To arm-wrestle

    Votes: 16 15.2%
  • Total voters
    105
Sander VF

Sander VF

The Fallen
Oct 28, 2017
26,780
Tbilisi, Georgia


The T. rex has everything an infamous apex predator needs like giant muscular legs and a powerful bite, however, the one area that this giant dinosaur doesn't deliver are with its arms, as they are famously small. So why did such a large and famous predators have such tiny forelimbs.
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So we can very reasonably infer WHY the arms of some Theropods became smaller over time. These reasons are laid out very well in the video, both for Theropods at large and T. rex in particular.

TL;DW: Tyrannosaur lineage was trending towards more and more robust skulls, culminating with T. rex and its massive noggin with the strongest bite of any land animal ever. Arms had to reduce in size to compensate for that added weight. In addition they had to make room for the massive neck muscles needed to support the head.

However, unlike the truly vestigial arms of Carnotaurus and other Abelisaurs, we have evidence that Tyrannosaur arms served SOME purpose (s). What this could have been is still a mystery.

One theory I've heard of that I don't think Moth Light Media covered is that they could've been used to hold onto prey as a leverage for a better bite.

BTW, you wouldn't be able to win an arm-wrestling match with a T. rex, its "tiny" arm could easily tear yours off. Those tiny arms were still RIPPED. T. rex was fucking swole from head to toe.
 
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Sander VF

Sander VF

The Fallen
Oct 28, 2017
26,780
Tbilisi, Georgia
pochi said:
Lmao I never thought of it but Trex were goofy.
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If T. rex were goofy due to small arms, then what about Abelisaurs?

rajasaurus_colour2_by_paleocolour-dbrnk53.jpg

abelisaurus-759.jpg

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These fuckers were probably a few million years of evolution away from not having arms at all.
 
Menome

Menome

"This guy are sick"
Member
Oct 25, 2017
6,761
If anything, their arms look slightly elongated in this picture 🤔

s7WcWXs.jpg
 
PinkCrayon

PinkCrayon

Member
Oct 25, 2017
1,278
Seeing one running at you would be scary enough, just imagine if it had jacked up gorilla arms too
 
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Sander VF

Sander VF

The Fallen
Oct 28, 2017
26,780
Tbilisi, Georgia
That slashing theory looks kinda silly when you visualize it lol, even though there is some reasoning behind it.

PinkCrayon said:
Seeing one running at you would be scary enough, just imagine if it had jacked up gorilla arms too
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That's the thing though.

Those arms WERE jacked, they were just tiny relative to the rest of the body.

Although if it had arms large relative to the rest of the body, it would probably fall over lol.
 
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TheEchosOfTheCyborg

TheEchosOfTheCyborg

Member
Feb 24, 2018
6,260
If I recall right, wasn't an aid to sex something early whales like Basilosaurus used their small vestigial hind limbs for?

Also Basilosaurus means King Lizard, because when they first found sea serpent like fossils, they assumed it had to be a whale only to actually be a reptile (Mosasaurus) and weren't going to make that mistake again... Only for it to be a whale the second time, can't imagine how they made that initial mistake:
Basilosaurus.jpg
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Jakisthe

Jakisthe

Member
Oct 25, 2017
5,887
Because can you imagine if those arms had been similarly proportional to it's legs? Would have been terrifying. Gigantic gorilla arms; perpetually leaning over; looking like it's about to punch through a tree or chokeslam a Triceratops.
 
Dan Thunder

Dan Thunder

Member
Nov 2, 2017
15,416
To make their penis look bigger.

They were probably pretty strong anyway so I imagine it was probably so there was just enough strength to hold onto prey. Massive arms would have been a waste and consumed unnecessary energy.
 
Ravelle

Ravelle

Member
Oct 31, 2017
18,968
They're basically big chickens right? Always thought they were more like the remnants of small Wings, the Wings part that withered away after millions of years when we found it and this is what was left.
 
Static

Static

Avenger
Oct 25, 2017
6,211
I guess I always just assumed that their ancestors were quadruped and they didn't need big strong arms, because their jaw does the work for them.
 
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Sander VF

Sander VF

The Fallen
Oct 28, 2017
26,780
Tbilisi, Georgia
Static said:
I guess I always just assumed that their ancestors were quadruped and they didn't need big strong arms, because their jaw does the work for them.
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Ancestors of all dinosaurs were indeed quadraped but they went biped very early on their evolution and then some dinosaur clades went back to being quadraped. T. rex ancestry was bipedal all the way. As they put more emphasis on their jaws, arms started getting increasingly deemphasized.
 
The Silver

The Silver

Member
Oct 28, 2017
11,015
They put all their skills points into bite force and didn't have enough left over for arm development.
 
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Sander VF

Sander VF

The Fallen
Oct 28, 2017
26,780
Tbilisi, Georgia
Ravelle said:
I'll take your word for it Mr Rex.

I wonder how stable the t-rex was, did he ever trip while in persuit and went face first in to the dirt?
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Preventing that was actually one of the reasons why those arms were small. As the head became larger and heavier, the arms became smaller so as not to make it too frontloaded.

In addition, this freed up space for larger neck muscles needed to hold up and wield that skull
 
softie

softie

Member
Oct 30, 2017
142
young t-rexes are like cute fluffy chicken-lizards, I'd never would like to arm wrestle with them, only hug.
t-rex-american-museum-natural-history-designboom-04.jpg

t-rex-american-museum-natural-history-designboom-03.jpg
 
Hyun Sai

Hyun Sai

Member
Oct 27, 2017
14,562
Because if they didn't, they would have smashed the meteor like Chris smashed the boulder.
 
formasymphonic

formasymphonic

Member
Oct 27, 2017
4,794
It's probably a combination of doing everything with their mouths anyway, and larger arms being a target when they fight with each other.

powerful jaws biting off a larger arm = more risk of blood loss and lower chance of survivability. Evolution could then favour those with smaller arms being less likely to get bitten off (or if they did lower blood loss and more chance of survival to mate regardless)
 
danmaku

danmaku

Member
Nov 5, 2017
3,289
Sander VF said:
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These fuckers were probably a few million years of evolution away from not having arms at all.
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Trey the explainer has a great video on Carnotaurus:



They were probably super fast predators, kinda like giant cheetahs. It's fascinating how totally different animals ended up playing similar roles in their respective environment. Carnotaurus didn't have a super powerful bite, compared to other predators of its time, so it probably attacked smaller animals that simply couldn't run away because it was so fast for its size.
 
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