STONY BROOK, N.Y., Nov. 5 (UPI) -- The skull of a groundhog-like mammal that lived 60 to 70 million years ago in the last epoch of the dinosaurs, discovered four years ago in what is now Madagascar, offers clues to the early evolution of mammals.
The well-preserved cranium is one of very few mammalian fossils recovered from this time period, a time when large, carnivorous dinosaurs dominated the food chain. The skull fossil belongs to a previously unknown mammal named Vintana sertichi, a member of a group of early mammals called gondwanatherians.
Researchers believe the almost entirely intact skull could offer new insights into the a group of early mammals which until now was evidenced only by teeth and jaw fragments.
"The discovery of Vintana will likely stir up the pot," Stony Brook University paleontologist David Krause, who led the research into the newly named mammal, said in a recent press release. "Including it in our analyses reshapes some major branches of the 'family tree' of early mammals, grouping gondwanatherians with other taxa that have been very difficult to place in the past."
The work of Krause and his colleagues was published this week in the journal Nature.
The finding "substantially expands our knowledge of the forms that mammals evolved during the Mesozoic, and the ecological roles they played," Anne Weil, an anatomy researcher at Oklahoma State University who authored an editorial appearing alongside the Nature study, told Discovery News.
The skull's strange array of features suggests Vintana was a shifty, large-eyed herbivore, outfitted with keen senses of hearing and smell. Vintana had to be quite agile to thrive in the lowland coastal floodplain of a the Late Cretaceous -- a landscape filled with sharp-toothed dinos, crocodiles and massive snakes. Most other mammals were mouse-sized, scurrying beneath the underbrush.
Vintana's discovery confirms that gondwanatherians are related to two other groups of early mammals called multituberculates and haramiyidans, helping to clear up researchers' previously murky conception of the evolutionary tree of early mammals.
Though Vintana is a member of a dead lineage, with no modern relatives, scientists say other related groups of early mammals were able to survive the extinction event that killed off the dinosaurs.