Researchers have discovered an almost complete skull of a previously unknown animal that was comparable to a giant groundhog and lived in dinosaur times.
The newly-discovered species, which lived in what is now Madagascar, could alter current theories about the evolution of early mammals, the National Science Foundation reported.
The new fossil, dubbed Vintana sertichi, belonged to a group of early mammals called gondwanatherians. Before the discovery of the fascinating skull there were only fragments of fossils from this group; the new find provides the first true insight into the lives of these ancient animals.
"We know next to nothing about early mammalian evolution on the southern continents," said Stony Brook University paleontologist David Krause. "This discovery underscores how little we really know. No paleontologist could have come close to predicting the odd mix of features this cranium exhibits."
The skull measured about five inches long, which is twice the size of the largest-known mammal skull from this region during the reign of the dinosaurs.
The initial discovery of the skull came about by accident. Joe Sertich, then of Stony Brook University, collected a 150-block rock matrix that was teeming with fish fossils. When a CT scan was performed on the block, a nearly complete skull was revealed to be inside.
"When we realized what was staring back at us on the computer screen, we were stunned," said scientist Joe Groenke of Stony Brook, the first to view the CT images.
The researchers then spent the next six months extracting the skull from the surroundings rock "one sand grain at a time."
The skull's teeth, eye sockets, braincase, and inner ear suggests it was most likely an herbivore with large eyes that had a powerful sense of smell and hearing. The animals, and other gondwanatherians , were most likely relatives of multituberculates.
Madagascar was an island for over 20 million years before the when Vintana first appeared. The researchers believe the primitive features of the skull are leftover from a time when the animals were marooned on the island, allowing them to evolve separately from species in Africa and Australia.
The findings were published in a recent edition of the journal Nature.
