 source NewScientist
A dinosaur family has been discovered which apparently lived and
died in an underground burrow. Palaeontologists say it is the first
solid evidence that dinosaurs lived in burrows and that adults cared
for juveniles long after they had hatched.
David
Varricchio of Montana State University in Bozeman, US, and colleagues
analysed bones from an dried old river floodplain in south-west
Montana. The bones were inside a twisting, worm-like deposit of
sandstone that passed through three distinct layers of rock.
Varricchio says the sandstone formed 95 million years ago when sand
washed into a burrow measuring more than 2 metres in length, 30
centimetres in width, and nearly 40 cm high. The dinosaurs inside had
apparently already died of unknown causes.
The burrow-dwelling dinosaurs were a previously unknown species of two-legged plant-eaters, which Varricchio has named Oryctodromeus cubicularis, meaning "digging runner of the lair".
Related
to the larger duck-billed hadrosaurs, they were part of a group called
hypsilophodonts. The adult was about 2.1 metres long, although more
than half of this was tail. The whole animal probably weighed 22 to 32
kilograms, Varricchio estimates. That means its body was about the size
of a modern coyote.
Bigger and meaner
Oryctodromeus
probably dug with its strong forearms and robust shoulders, and may
have pushed dirt with its snout. "At first it seemed too big for the
burrow," says Varricchio. However, modern mammals squeeze into tight
places for protection, he reasons. "A tight fit precludes anyone meaner
or bigger from getting in there," he told New Scientist.
The
adult had sheltered with two juveniles about half its length in a den
at the base of the burrow, originally covered by half a metre of earth.
Other small dinosaurs may also have dug burrows, says Varricchio, who had studied a closely related dinosaur called Orodromeus.
"In a couple of cases we found tight packages of bones in floodplain
environments, which is odd because bones should have gotten scattered"
if they were on the surface, but would have stayed together in a
burrow, he says.
"The
find is utterly stunning," says David Fastovsky at the University of
Rhode Island in the US, because it convincingly demonstrates a
behaviour previously unknown in dinosaurs. It also bolsters the case
that dinosaurs gave their young extended care, like their distant
descendants, modern birds.
Jeff Hecht
source NewScientist
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