By Paul Rincon
Science Reporter, BBC News
Palaeontologists have pieced together the fossilised skull of the oldest example yet found of a woolly rhinoceros in Europe.
The 460,000-year-old skull, which was found in Germany, had to be reconstructed from 53 fragments.
The extinct mammals reached a length of three-and-a-half metres in adulthood and, unlike their modern relatives, were covered in shaggy hair.
Details of the work appear in the journal Quaternary Science Reviews.
The team says the find from Germany fills a gap in our understanding of how these animals evolved.
First on the scene
"This is the oldest woolly rhinoceros found in Europe," said Ralf-Dietrich Kahlke, from the Senckenberg Research Institute in Weimar, Germany.
He added: "It gives us a precise date for the first appearance of cold-climate animals spreading throughout Asia and Europe during the ice ages."
The skull was pieced together from 53 fragments
The skull was discovered around 1900, in a gravel pit at the foot of the Kyffhauser mountain range near the city of Bad Frankenhausen.
But for more than one hundred years, no one ventured to put the pieces together until Dr Kahlke and his colleague Frederic Lacombat, from the Crozatier Museum in Puy-en-Velay, France, made their recent reconstruction.
After examining the cranium, they assigned the specimen to Coelodonta tologoijensis, an Asian woolly rhino species that had not previously been described in Europe.
Woolly rhino (Coelodonta) first appeared about 2.5 million years ago in the northern foothills of the Himalayas.
And for much of their evolutionary existence, these mammals were confined to steppe environments in continental Asia.
The key was their diet, which started off being rather mixed - including the leaves of shrubs and trees.
But as conditions became increasingly arid, the woolly rhino evolved into a specialist in browsing for steppe food that grew nearer to the ground.
Changes in the animals' anatomy enabled them to tolerate cold, arid conditions
The animals probably migrated from Asia into East and Central Europe when cold, arid conditions held sway between 478,000 and 424,000 years ago.
Their territorial advances were paralleled by changes in anatomy.
"Analysis of the Frankenhausen specimen shows that Coelodonta tologoijensis... carried its head low along the ground and had a lawnmower-like mouth with a huge set of grinding teeth," said Mr Lacombat.
"As the climate became colder, these animals became more efficient at utilising the available food."
The researchers propose that the species represented at Bad Frankenhausen, C. tologoijensis, was ancestral to the "true" woolly rhino, C. antiquitatis, which was common across Eurasia during ice ages.