Dinosaurs that roamed Madagascar more than 66 million years ago had a most unusual fuzzy mammal living in their shadows—one so large, and with such strange features, that scientists say they could have never predicted its existence.

That is, until 2010, when a team of scientists looking for fish fossils accidentally collected its nearly complete skull from a site along Madagascar's west coast.

Since then, researchers have learned that the groundhog-like critter had supersensory capabilities, with a large portion of its brain devoted to smell, and that it weighed about 20 pounds (9 kilograms)—much more than most mammals alive during the age of the dinosaurs.

"Not only does it have bizarre features, it's bizarre in being so humongous," says vertebrate paleontologist David