Endoceras

Geologic age: About 450 million years ago, Ordovician Period

Region in Minnesota: Minneapolis-St. Paul area

Fast fact: These impressive animals could reach up to 10 feet in length, making them some of the largest animals alive at the time. They likely sported 10 arms (but without suckers) and roamed the warm, shallow sea looking for food on the muddy seafloor. The Science Museum of Minnesota has a large Endoceras fossil on display that was found by a local collector!