The age of the dinosaurs is known for its giant reptiles. As an adult, the infamous Tyrannosaurus rex weighed over 6 tons—about as heavy as a city bus. But T. rexes were smaller teenagers before they grew into gargantuan adults.
“If you were to hop into a time machine and go to the Cretaceous period (145 to 65 million years ago), you’d be much more likely to see a teenage T. rex as opposed to an adult,” says Katlin Schroeder, a Ph.D. candidate in biology at the University of New Mexico. Not only were these teenage meat-eating dinosaurs abundant, Schroeder’s team found that they likely played an important role in the food chain.