New study says T. rex had tiny arms because of its skull

(CNN, KYMA) - We all know the Tyrannosaurus rex (T. rex) can't do push-ups or clap, but many people have wondered why the king of the dinosaurs had such puny arms.

It's a topic researchers have debated for decades with no real consensus. Now, a new study has its own theory: Big arms were a trade-off.

The study says the T. rex evolved to have an extremely strong skull, and since evolution tends to prefer perfecting one feature at at time, it came at the expense of upper body strength.

T-rex simply didn't need strong arms when he could kill just about anything by head butting it.

The hypothesis appeared last week in the journal "Proceedings of the Royal Society B." To learn more about the study, click here.