New remains from the region suggest that at least some dinosaurs likely roosted together to sleep, quite possibly as a family, much like many modern birds do today, researchers said.
This new evidence for dinosaur roosting stems from a confiscated fossil block that was illegally exported from Mongolia, which preserved the remains of three juvenile dinosaurs known as Oviraptorids (part of the bird line of dinosaur evolution), they said.
These three dinosaurs represent the same species that were roughly the same age, preserved in a sleeping posture, so close to each other that they would have been touching, in life.
Known as "communal roosting", this behaviour is seen in many birds today including chickens and pigeons.
"It is a fantastic specimen. It is rare to find a skeleton preserved in life position, so having two complete individuals and parts of a third is really incredible," said Gregory Funston of the University of Alberta in Canada.
Other fossils found in Mongolia also seem to belong to this new species, and further flesh out the life history of these animals, researchers said.
The notable head crest is present even at a young age, but the dinosaurs would have had gradually shorter tails as they aged, and some of their bones fused across their lifetime.
Their head crests and tails have been argued to represent sexual display features used in mating, somewhat similar to modern peacocks or turkeys.
"The origins of communal roosting in birds are still debated, so this specimen will provide valuable information on roosting habits in bird-line theropods," Funston added. The finding was presented at the annual meeting of the Society of Vertebrate Paleontology in Alberta, Canada.