While trilobites were prolific, they probably didn’t exactly rule the ancient seas. Trilobite, any member of a group of extinct fossil arthropods easily recognized by their distinctive three-lobed, three-segmented form. There must have been some predator who thought they would make a tasty lunch, but who could it have been? Trilobite fossils are particularly abundant and well-preserved in Ordovician rocks that crop out in southwestern Ohio. Mega paleontology Trilobites Fossils Cambrian Science History. Doctor Who actor Tom Baker honoured by scientists who name a 450 million-year-old trilobite after him. Trilobites are a class of extinct arthropod marine creatures. The rests of trilobites are met only in the sea sediments of Paleozoic era. Ordovician trilobites are so various, that their “morphological palette” has no analogues among either other trilobites, or other groups of arthropods as a whole (except for insects). Fossils of animals that drifted in the upper layers of the ocean are particularly useful as index fossils, as they may be distributed all over the world. Trilobites (ToL: Trilobites