'Saber-Toothed Squirrel': First Known Mammalian Skull from Late Cretaceous in South America
Paleontologist Guillermo Rougier, Ph.D., professor of anatomical sciences and neurobiology at the University of Louisville, and his team have reported their discovery of two skulls from the first known mammal of the early Late Cretaceous period of South America. The fossils break a roughly 60 million-year gap in the currently known mammalian record of the continent and provide new clues on the early evolution of mammals.
The new critter, named Cronopio dentiacutus by the paleontologists, is a dryolestoid, an extinct group distantly related to today's marsupials and placentals.
Cronopio was shrew-sized, about 4-6 inches in length, and was an insectivore with a diet of the insects, grubs and other bugs of the time. It lived when giant dinosaurs roamed Earth -- more than 100 million years ago -- and made its home in a vegetated river plain.
The skulls reveal that Cronopio had extremely long canine teeth, a narrow muzzle and a short, rounded skull. "These first fossil remains of dryolestoids … give us a complete picture of the skull for the group," John R. Wible, Ph.D., curator of mammals at the Carnegie Museum of Natural History, said. "The new dryolestoid, Cronopio, is without a doubt one of the most unusual mammals that I have seen, extinct or living, with its elongate, compressed snout and oversized canine teeth. What it did with that unusual morphology perhaps may come to light with additional discoveries… ."
Rougier describes Cronopio in a manner that fans of a popular animated movie series can easily understand.
"It looks somewhat like Scrat, the saber-toothed squirrel from 'Ice Age,' " he said.