(Reconstruction of Cronopio dentiacutus in its native environment. Artist: Jorge Gonzalez / copyright: Guillermo Rougier)
Northern Patagonia was once home to a squirrel-like mammal with extremely long canine teeth, a petite 4 to 6-inch-long body, a narrow muzzle and a rounded skull, according to a paper in the latest issue of Nature.
You won't see this critter stealing birdfood in your garden because it lived more than 100 million years ago when dinosaurs were still thriving. As you can see from the above image, dinos must have been no strangers to this saber-toothed animal that might have spent its days darting around columnar dino legs.
The discovery breaks a prior gap of about 60 million years in the fossil record for South American mammals.
University of Louisville paleontologist Guillermo Rougier and co-authors Sebastián Apesteguía and Leandro Gaetano named the new animal Cronopio dentiacutus. It is a dryolestoid, an extinct group of animals distantly related to today's marsupials and placentals.
"It looks somewhat like 'Scrat,' the saber-toothed squirrel from 'Ice Age,'" Rougier was quoted as saying in a UofL press release. He's a professor of anatomy and neurobiology there.
Real life is often more bizarre than fiction.
"The new dryolestoid, Cronopio, is without a doubt one of the most unusual mammals that I have seen, extinct or living," said John Wible, curator of mammals at the Carnegie Museum of Natural History.
The researchers found skulls of the Scrat-like animals embedded in rock in a remote area of northern Patagonia, about 100 miles from the city of Allen in the Argentinian province of Rio Negro. It took the team several years of patient lab work to remove the specimens from the rocks.
"We knew it was important, based on the age of the rocks and because we found skulls," Rougier said. “Usually we find teeth or bone fragments of this age. Most of what we know of early mammals has been determined through teeth because enamel is the hardest substance in our bodies and survives well the passage of time; it is usually what we have left to study."
"The skull, however, provides us with features of the biology of the animal," he continued, "making it possible for us to determine this is the first of its kind dating to the early Late Cretaceous period in South America. This time period in South America was somewhat of a blank slate to us. Now we have a mammal as a starting point for further study of the lineage of all mammals, humans included."
A lot of paleontologist eyes are now on South America.
"… Until now, all we have had are isolated teeth and a few jaw fragments … which don't really help much in deciphering broader relationships," said Rich Cifelli, presidential professor of zoology at the University of Oklahoma and a researcher, who, like Rougier, has spent his career discovering and identifying mammal remains.
"The new fossils provide a sort of Rosetta Stone for understanding the genealogy of early South American mammals, and how they fit in with those known from northern landmasses," Cifelli said.
"Now," Cifelli concluded, "the burden is on the rest of us to find similarly well preserved fossils from elsewhere, so that the broader significance of Rougier's finds can be fully placed in context."