Why did the fearsome T-rex have such tiny arms?
This is Sandra Tsing Loh with the Loh Down on Science.
Finally, this age-old question has an answer! All with the help of Charlie Scherer and team from University College London.
They studied the evolution of almost ninety different carnivorous, two-legged dinosaurs. T-rexes included! Specifically, they looked at forelimb, body, and skull changes.
What they found? Smaller arms correlated with SIGNIFICANT increases in body size and skull thickness! Increases in dino body size also tracked with hunting larger prey!
Hunting bigger prey likely meant relying more on their jaws, with no more need for arms! As they say, use it or lose it.
A million years in the making… Mystery solved!
Scherer, C. R., Steell, E., & Upchurch, P. (2026). Drivers and mechanisms of convergent forelimb reduction in non-avian theropod dinosaurs. Proceedings of the Royal Society B Biological Sciences, 293(2071). https://doi.org/10.1098/rspb.2026.0528