Why did T. rex and Other Dinosaurs Have Tiny Arms

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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[GarryDKing]

it really puts things in perspective that, while T rex has tiny arms, its arms are still longer than our own arms.

[pontusloviken]

Was the arm more balanced when the T-Rex was younger? Every dinosaur had to start from the size of an egg, and maybe it played a role in the child/adolescent stage of the T-Rex's life?

[Grand_History]

Since reading the book “good enough”, I’ve realized not every trait is an adaptation selected for because of pressures. A lot of things happen in nature that just persist because they are good enough not to be eliminated. Nature is actually pretty forgiving, and a more accurate term than “natural selection” is “natural elimination”. Maybe the short arms came first and a purpose was made after. Or maybe in cohesion. Animals tend to do what they can with the limbs they have.

[funkyfetus]

“These tiny arms could be terrifying weapons” is a really funny sentence

[jasonshallcross]

"*stumped* scientists for years" - lol

[Beroka]

why need arms when you have that much swag

[jtj]

body part proportions change with age. In a newly hatched T. Rex, the forearms may have been proportionately larger, and served to help grasp and tear off smaller pieces of food. The arms would be closer to the mouth in the baby T. Rex. Maybe.

[WaterShowsProd]

There was a recent imprint discovered of a Tyrannosaurs having pushed itself up using its forelimbs after squatting to eat.

[Gzeebo]

I have often wondered if T-Rex's arms were truly vestigial, maybe even fully internal to the body like a whale's leg bones. Your explanation about nerve fibres and muscles helped me understand how scientists can tell they were actual arms.

[CountJeffula]

I wonder if it could have helped them turn their eggs or arrange their nest. I can’t imagine how else they could manage something so delicate.

[afkfromawake]

What's this? My favorite Paleontology Youtuber is back?


Wonderous upon wonder!

[robertmcauslan]

Most "walking" birds have the ability to run up trees to escape predators before flight feathers come in. Hoatzin climb around tree branches using wing claws. Perhaps young rexes used the arms in similar ways until they reached a size too big for most predators. Even bears and lions climb trees before they become too bulky.

[brianedwards]

Two ideas: One, they had feathers of some kind on their arms and the muscles were needed to perform mating displays. Two, they were needed to gather nesting material to cushion the fall of the egg from a cloaca 10 feet off the ground. The inward facing claws are like the hooks on the end of bungee straps holding vegetation to the chest as the animal returns to the chosen site.

[larvid]

Has anyone considered that the arms may have been in larger use during the animals younger growth stages?

[siyacer]

Something about your videos is so relaxing, I can't help but fall asleep even though it genuinely interests me

[Werrf]

Display structures. Yeah, I know, it's the go-to nowadays, so sue me. But imagine Rexy having a line of bright iridescent feathers on each arm. When he's trying to impress a mate, he holds out his arms, fans his feathers, and wiggles those two claws to make the fan shimmy around, peacock-style.

[desmonddesjarlais]

Somewhere out there a little fossilized piano waits to be found

[Taneth]

Would be interesting to find out if there were feathers on the arms, as we know therapods did have them, that maybe made them appear larger and could be used for temperature regulation or displaying colours.

[Clearlight]

Damn. If I had been cornered by a T-Rex my strategy would have been to challenge him to an an arm wrestle and let me go if I win.
Now it seems even that's not gonna work.

[S-T-E-V-E]

It would be interesting to discuss where Dinosaur evolution was heading before the Yucatan ELE? Could you do a video?