Which dinosaurs have hollow bones?

But studies have shown that Allosaurus, a fairly primitive theropod, also had hollow bones. Allosaurus was a big animal with tiny arms, so it wasn’t flying anywhere—like so many other bird traits, hollow bones appear early in the dinosaur family tree.

Why were T-rex bones hollow?

Fossil bones show air pockets for high-energy lifestyle. Dinosaurs’ hollow bones may have given them the puff to lead active lifestyles. A fossil find shows that the group of dinosaurs that included Velociraptor and Tyrannosaurus rex probably used the same super-efficient respiratory system that birds have today.