What are they? They are invertebrates (creatures without backbones). These small marine animals grew in groups, in a variety of shapes and sizes – mound-shaped, lacy, tree-shaped, or even screw-shaped. When did it live? Sometime in a period from 345 to 315 million years ago. Is this type of creature extinct? No. Where did it live? They spent their lives attached to the sea floor, stones, or to other animals. How did it eat? What did it eat? The creatures had hairlike tentacles which beat to and fro in the water, producing currents that carried food to the body where it could be swallowed.