A burrow photographed from above, showing a cross section, with the entrance on the right sideThe world's oldest dinosaur burrows have been discovered in Australia.
Three separate burrows have been found in all, the biggest 2m long, each built to a similar design and just big enough to hold the body of a small dinosaur.
The 106-million-year-old burrows, the first to be found outside of North America, would have been much closer to the South Pole when they were created.
That supports the idea that dinosaurs living in cold, harsh climates burrowed underground to survive.
The only other known dinosaur burrow was discovered in 2005 in Montana, US.
Described two years later, this burrow dated from 95 million years ago and contained the bones of an adult and two juveniles of a small new species of dinosaur called Oryctodromeus cubicularis.
 |  It provides an alternative explanation for how small dinosaurs might have overwintered in polar environments  Palaeontologist Anthony Martin |
Now the older burrows have been found by one of the researchers who made the original Montana discovery.
"Like many discoveries in palaeontology, it happened by a combination of serendipity and previous knowledge," says Anthony Martin of Emory University in Atlanta, Georgia, US.
"In May 2006, I hiked into the field site with a group of graduate students with the intention of looking for dinosaur tracks. We did indeed find a few dinosaur tracks that day, but while there I also noted a few intriguing structures."
Martin returned to the site, a place dubbed Knowledge Creek that lies 240km from Melbourne, Victoria, to study these structures, once in July 2007 and again in May this year.
His first reaction was one of astonishment.
"I was scanning the outcrop for trace fossils, and was very surprised to see the same type of structure I had seen in Cretaceous rocks of Montana the previous year," says Martin.
That original structure turned out to be the burrow of O. cubicularis, which Martin described with colleagues David Varricchio from Montana State University, Bozeman, US, and Yoshi Katsura of Gifu Prefectural Museum in Seki City, Japan.
"So to walk up to the outcrop and see such a strikingly similar structure, in rocks only slightly older, but in another hemisphere, was rather eerie."news source- http://news.bbc.co.uk/earth/hi/earth_news/newsid_8144000/8144199.stm
