Dinosaur-age Argentinian mammal discovery

From New Scientist:

Sabre-toothed squirrel scurried at dinosaurs’ feet

18:00 02 November 2011 by Colin Barras

Truth is sometimes just as strange as fiction. Palaeontologists have unearthed fossils of a bizarre mammal that lived in the shadow of the dinosaurs and was a dead ringer for the sabre-toothed squirrel star of the computer-animated Ice Age films.

Mammals were a fixture of the dinosaur era, but their remains are rarely preserved. The new fossil, which comes from 95-million-year-old rocks in Argentina, is a tantalising sign of what we are missing. Its 2-centimetre-long skull has large eye sockets, a narrow snout and a formidable pair of long canines unlike anything seen before in Mesozoic mammals.

At the time this creature, dubbed Cronopio, roamed Earth, the marsupial and placental mammals that dominate today had already begun to branch out. But Cronopio was a more primitive beast. Its discovery confirms that early mammals tried out body shapes for which no living parallel exists, says Guillermo Rougier at the University of Louisville in Kentucky, whose team made the find.

Cronopio was dug out of rocks rich in the remains of giant sauropod and theropod dinosaurs. Its large eye sockets indicate it was possibly nocturnal, says Christian de Muizon at the Museum of Natural History in Paris, France, who was not a member of Rougier’s team. “The function of the long canines is difficult to assess,” says Rougier. “There is no real modern model for that.”

The shape of the squirrel’s molars suggests that it may have had a taste for insects, he adds. Rougier named the fossil after fictional characters in the novels of Argentinian writer Julio Cortázar, but he is well aware of its silver screen doppelgänger. “Some ridiculous-looking cartoon characters can sometimes be found later as real fossils,” he says.

Journal reference: Nature, DOI: 10.1038/nature10591.

See also here. And here. And here.

Recently announced findings, published in the journal Science by Maureen O’Leary and colleagues, represent an important step in understanding the early evolution of placental mammals, and sheds light on its relation to the mass extinction of dinosaurs. The scientists report that the majority of living mammals evolved at an explosive rate following the extinction of the dinosaurs some 65 million years ago: here.

Related articles

• Placental mammals evolved from small bug eater (futurity.org)
• Vote: What Would You Name Squirrelly Mammal Ancestor? (livescience.com)
• Furry, cute, long-tailed and distinctly rodent-like – the creature that could be our earliest human ancestor (independent.co.uk)
• The Missing Link: Scrat! No, Really! (formingthethread.wordpress.com)
• Ancestors of today’s placental mammals may never have shared the Earth with dinosaurs (sciencenews.org)
• Meet Your Mama: First Ancestor of All Placental Mammals Revealed (livescience.com)
• Meet our earliest common mammalian ancestor (newscientist.com)
• Dino die-off ‘a big bang’ for mammal life (stuff.co.nz)
• The orders of modern placental mammals originated after the extinction of the dinosaurs (whyevolutionistrue.wordpress.com)
• Placental mammal diversity exploded after age of dinosaurs (phys.org)