Meet your ancestor: This small and furry scampering insect-eater lies at the base of the family tree for humans and most mammals, according to the largest-yet study of mammalian evolution.
The agile animal is the earliest among placental mammals -- the largest branch of the mammal tree consisting of more than 5,100 living species. Only marsupials, such as kangaroos, and monotremes (egg-laying mammals including the platypus and echidna) fall outside of that huge group.
The mammal "had a diet of insects, a fleshy nose, a light underbelly in its fur, and a long tail," said Maureen O'Leary, an associate professor in the Department of Anatomical Sciences in the School of Medicine at Stony Brook University. O'Leary was lead author of a study about the mammal in the latest issue of Science.
"It was larger than a mouse, but smaller than a rat," added O'Leary, who is also a research associate at the American Museum of Natural History "As for its bones, it lacked special bones that are found near the pelvis, and in its ear had a small bone for hearing that was shaped like a stirrup."