The 95-million-year-old fossil remains of small dinosaurs have been unearthed in a chamber at the end of a sediment-filled tunnel in Montana. But these aren't like other dinos. These animals actually constructed the 2-mile long tunnel in which they were found.

The adult and two juveniles had burrowed into the ground, proving for the first time that some dinosaurs dug dens and cared for their young in such structures, reports the BBC News. "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 from Montana State University and his colleagues wrote in the journal Proceedings of the Royal Society B. The dens may have also allowed them to survive the initial disaster that felled other dinosaurs and led to their extinction.

The type of dinosaurs found in Montana have never before been seen and so have been given the scientific name Oryctodromeus cubicularis, which means "digging runner of the lair." These animals were made to dig. Their snout, shoulder girdle and pelvis all have features that helped them to burrow. Compared to other dinosaurs, the Oryctodromeus cubicularis was small. The adult measured about 6.8 feet from nose to tail, and most of that was in the tail, which was 3.9 feet long.

Almost as fascinating as the fossil remains of this new type of dinosaur is the tunnel structure in which it lived. The tunnel was actually constructed by the dinosaur. Varricchio says it was sloping and had two sharp turns before ending in the chamber, making it similar to the dens of modern burrowers, such as the striped hyena, puffin and some rodents, reports the BBC.

Many would have missed the significance of the tunnel, insists Dr. Kevin Padian from the Museum of Paleontology at the University of California, Berkeley. "This discovery is first and foremost a testament to the value of keeping one's eyes open in the field and noticing everything, and it took a special group of scientists to realize the meaning of the discovery that they made," he told the BBC.

--From the Editors at Netscape