Small dinos burrowed to avoid winter's chill

London, July 14 (ANI): The discovery of three fossil burrows in south-eastern Australia has suggested that small dinosaurs living in polar areas survived the lean months when little food was available by burrowing during the winter.

According to a report in New Scientist, fossils from "Dinosaur Cove" in Victoria show that small plant-eating dinosaurs called hypsilophodontids were common in the area about 110 million years ago, a time when the region was within the Antarctic Circle.

The region was forested, with temperatures 6 or 7 degrees Celsius warmer than such latitudes are today.

But, with the sun below the horizon for weeks or months of the winter, fresh vegetation would have been lacking.

Plant-eating dinosaurs had been thought to avoid the dark season by migrating long distances.

The evidence for this was based on fossils from another related species, Edmontosaurus, which have been found from northern Alaska to Montana.

However, last year, Eric Snively of the University of Alberta in Edmonton, Canada, showed that the fossils could have been from a number of species, or that the dinosaurs may have lived at different times.

Burrowing would have given small dinosaurs a refuge for the winter where they could rest and conserve energy, but evidence of this had been lacking.

Then, two years ago, David Varricchio of Montana State University in Bozeman described a fossil burrow in Montana that contained the remains of one adult and two juvenile hypsilophodontids similar to those found in Australia.

Tony Martin of Emory University in Atlanta, Georgia, says that working with Varricchio on the Montana burrow primed him to spot the new burrows when he went to Australia looking for dinosaur tracks.

"I turned around a corner at the outcrop, and I saw a structure identical to the one I saw in Montana," he said.

Further investigation uncovered a total of three burrows in the area, each very similar to those in Montana.

Cross-sectional measurements of a corkscrew-shaped burrow 2.1 metres long suggest that it was dug by dinosaurs weighing 10 to 20 kilograms - the same size as the Montana burrow-diggers.

According to Martin, the burrows were dug in soil deposited in a valley by massive spring floods of meltwater similar to those seen today on the north slopes of Alaska.

The dinosaurs could have lived in the burrows in autumn and winter, but would have had to move out before the following year's spring floods filled them with fresh sediment. (ANI)