Stony Brook scientists say a bizarre 66-million-year-old mammal has been discovered in Madagascar by a team of international researchers led by Dr. David Krause, senior curator of vertebrate paleontology at the Denver Museum of Nature & Science and professor emeritus at Stony Brook University.

The discovery of the opossum-sized mammal that lived among dinosaurs and massive crocodiles on the fourth largest island on Earth was announced in the journal Nature.

Dr. James B. Rossie, of Stony Brook University, is one of the study’s co-authors. The late Yaoming Hu, of Stony Brook University, was also a co-author.

The finding of the new mammal, called Adalatherium, is based on a nearly complete skeleton that is astoundingly well preserved. The skeleton is the most complete for any Mesozoic mammal yet discovered in the southern hemisphere.

“Knowing what we know about the skeletal anatomy of all living and extinct mammals, it is difficult to imagine that a mammal like Adalatherium could have evolved; it bends and even breaks a lot of rules,” Krause said.

The teeth of Adalatherium are vastly different in construction than any known mammal. Its backbone had more vertebrae than any Mesozoic mammal, and one of its leg bones was strangely curved.

About the size of a Virginia opossum, Adalatherium was also unusual in that it was very large for its day; most mammals that lived alongside dinosaurs were much smaller, mouse-sized on average.