We know a great deal about non-avian dinosaurs from the bones and trace fossils they left behind. But those aren’t the only sources of information we have about the Mesozoic superstars. Paleontologists frequently turn to modern animals to better understand the anatomy and even the behavior of extinct dinosaurs. Unified through evolutionary theory, the traits of living animals can help us fill in the spaces between fossil bones.

Dinosaurs had muscles, stomachs, hearts, lungs, blood, and more. We know most of these things not because of direct evidence – preserved soft tissues are hard to come by in the fossil record – but because non-avian dinosaurs were vertebrates that shared a common ancestry with animals alive today. They had the same