Invertebrates, the animals without backbones, first appeared on the Earth during the Cambrian period. The most common early animals were arthropods, the trilobites. They were soft-bodies animals living mostly in the sea. Another important fossils of invertebrates found during the Paleozoic time were molluscs, echinoderms, crinoids (sea lilies: cup-shaped body), starfish and corals. Fossils of these animals were found all over the world including some parts of Antarctica.
Fossil Animals: Invertebrates
