Aren't these trilobites cool? Trilobites are extinct, hard-shelled marine animals that lived in the seas even before the dinosaurs. Trilobites were very common and very diverse; over 15,000 species of trilobites are known. Some trilobites crawled along the sea floor, some swam, and others drifted with ocean currents. The different trilobite species probably had different diets; some were herbivores (eating plants), some were detrivores (eating decayed material) and some were scavengers (eating carrion). We have these trilobites on sale in our giftshop and in display in our prehistoric museum.