What is it? It was an invertebrate (a creature with no backbone). Its body was contained in a shell that had two parts, or valves. When did it live? Sometime in a period from 345 to 315 million years ago. Is this type of creature extinct? No. Oysters, mussels, and clams are living types. Where did it live? Nearly all fossil forms were marine. Most lived on the sea floor. How did it eat? What did it eat? It ate microscopic creatures from the water. They were drawn into the creature’s shell using a “foot” which it exposed by opening its shell, and another part of its body called a siphon.