Dinosaurs didn’t just walk the Earth during the Mesozoic. They also burrowed into it. Since 2007, paleontologists have known that some small, beaked, herbivorous dinosaurs created underground dens.

“It’s odd that dinosaurs didn’t really [burrow], as it’s a common way of life among lizards and snakes,” paleontologist Paul Barrett told BBC Future. “Given more time, some dinosaurs ...