A veggie-eating mammal appropriately named "Luck" somehow managed to live alongside several large carnivorous dinosaurs in Madagascar during the Late Cretaceous, according to a new study.
The 66-70-million-year-old mammal, described in the latest issue of the journal Nature, is one of the largest known Dinosaur Era mammals. Named Vintana ("Luck") sertichi, it weighed about 20 pounds, or roughly twice the size of a modern day groundhog, which it resembled.
"This is enormous for a Mesozoic mammal, most of which were shrew or mouse-sized, living in the shadow of dinosaurs," project leader David Krause told Discovery News.
"There were both large (such as Majungasaurus) and small (such as Masiakasaurus and Rahonavis) carnivorous dinosaurs that lived alongside Vintana, not to mention large sauropod dinosaurs (Rapetosaurus, Vahiny), seven different types of crocodiles, both large and small snakes, a giant frog, 6–7 species of birds, a lizard, several fishes and more," added Krause, who led the research and is a professor in the Department of Anatomical Sciences at Stony Brook University.
Joseph Sertich, a former graduate student of Krause's, found Vintana's nearly complete cranium by fortuitous accident in a sandstone block otherwise filled with fish fossils. The block was unearthed in what is now Madagascar.
The cranium represents the first such fossil ever discovered for any gondwanatherian mammal. "Gondwanatherian" refers to an early group of mammals that previously were among the most enigmatic of all prehistoric animals.
Comprehensive analysis of Vintana's teeth, eye sockets, nasal cavity, braincase and inner ears reveals that it was a toothy and agile large-eyed animal with keen senses of hearing and smell.
The researchers had never seen anything comparable to this skull before, however.
"Throw together some anatomical features from ancient mammal-like reptiles, Pleistocene ground sloths, an extant rodent, and maybe a few bits and pieces from the Muppets on 'Sesame Street' and you might get something that resembles the cranium of Vintana," Krause said.
However unusual, the herbivorous animal managed to scurry around its treacherous-carnivore landscape. At the time, the area where it lived was a lowland coastal floodplain.
Vintana shows that gondwanatherians are related to two other early groups of mammals known as multituberculates and haramiyidans. Together, they form a larger group called Allotheria.
Because haramiyidans, which date back to the Late Triassic, are now classified as being in Allotheria, the origin of mammals has just been pushed back by about 25 million years.
"Luck" has therefore proven to be a very lucky find for paleontologists, and the animal might have been lucky in life too. Krause said it is possible that it might have survived the mass extinction event that wiped out all of the non-avian dinosaurs, although fossils confirming that have not yet been found. Other gondwanatherians are known to have survived the extinction around 65 million years ago, perhaps by hibernating underground.
Anne Weil, an associate professor of anatomy at the Oklahoma State University Center for Health Sciences, authored an accompanying "News & Views" article in Nature. She told Discovery News that Vintana "substantially expands our knowledge of the forms that mammals evolved during the Mesozoic, and the ecological roles they played."
Both she and Krause shared that "Luck" has no living descendants.
It instead was, as Krause said, "an early evolutionary experiment in mammalness."