Brachiopods

Brachiopods are a group of invertebrate organisms that were widely distributed in geological history. Today, they only play a minor role among the ground-dwelling marine animals. While Brachiopods show a resemblance to bivalves, they are not closely related. Especially in the Paleozoic, they displayed a large diversity of rapidly changing forms, which makes them well-suited for use as index fossils (“time markers”).