U.S. scientists found 95-million year old fossils of dinosaurs in Montana. The special thing about these dinosaurs is that they dug dens in the ground:
The researchers say the discovery is the first definitive evidence that some dinosaurs dug dens and cared for their young in such structures.
"Burrowing also represents a mechanism by which small dinosaurs may have exploited the extreme environments of polar latitudes, deserts and high mountain areas," Dr David Varricchio and colleagues tell the publication.
The Montana dinosaurs have not been seen by palaeontologists before and have been given the scientific name Oryctodromeus cubicularis, meaning "digging runner of the lair".