First Evidence Of Burrowing Dinosaurs Found

Scientists have unveiled the first evidence of burrowing dinosaurs.

A 95 million-year-old set of fossils, unveiled for the first time today in a report in Proceedings of The Royal Society journal, reveals the existence of a previously unknown type of dino that made a snug home in the ground.

They comprise the preserved remains of a caring dino family, found in an underground den in Montana, America.

They are the first burrowing dinosaurs ever discovered. Scientists say the 2.1m-long lizard would have raised its young in burrows and used them to shelter from extreme weather, so they could live in harsh environments such as the arctic regions and deserts.

The find also casts doubt on the theory that a giant asteroid from space that crashed into the earth wiped out the dinosaurs.

It is thought that the dinos died out because they did not have shelter, unlike burrowing creatures that survived past the Cretaceous age, but according to this assumption, the burrowing dino should also have survived - yet has not been found after the period the asteroid is meant to have hit Earth.

Named Oryctodromeus cubicularis, which translates as 'digging runner of the den', the dino, a herbivore, was ideally adapted to its life in the Cretaceous-period.

Its snout was shovel-shaped to help it shift earth, while large bony shoulders, provided attachments for powerful muscles used to burrow, while a strengthened hip helped brace the creature during digging.

However it also had unusually long hind legs for a burrower, so it could take off at speed if threatened far from its underground labyrinth.

The fossils of an adult and two juvenile dinos were found in a 2m-long burrow, with a large chamber, 50cm underground, linked to the surface by a narrow 30cm-wide tunnel.

The bones are from a 2.1m-long adult, and two 1.3m-long youngsters, which suggests a strong family bond, say scientists.

Dr David Varricchio, of Montana State University who led the research, said: "Vertebrates burrow for a variety of reasons: to find food, escape predators, and avoid harsh environmental conditions.

"Burrowing may have been an important adaptation for the rearing of young. Burrowing also represents a mechanism by which small dinosaurs may have exploited the extreme environments of polar latitudes, deserts and high mountain areas.

"[The discovery] uniquely preserves both an adult-young association and direct evidence of denning in the form of a dwelling trace.

"Although growth rates were probably fast, the large size of the juveniles suggests that the parent-young bond persisted for a minimum of several months."

However, the discovery may lead to confusion among scientists, as Dr Varrichio claims it questions the theory of dinosaur extinction.

He continued: "By denning, small dinosaurs could have potentially withstood severe conditions, such as aridity, drought and daily or seasonal temperature extremes.

"Such behaviour would have allowed dinosaurs to occupy high mountains, desert environments and polar regions.

"Survivability of terrestrial vertebrates at the end-Cretaceous event has been attributed to sheltering behaviour, with the extinction of non-avian dinosaurs resulting from their inability to find an appropriate cover.

"Burrowing dinosaurs would challenge this argument, but these are yet to be found in the latest Cretaceous formations."