Description

Trilobites are hard-shelled, segmented members of Arthropoda and the class Trilobita that existed throughout almost all of the Paleozoic era, flourishing in the earlier part of it and slowly declining in the later part. The most common trilobites were about 2-7 cm (1-3.5 in) in length, but over their long history they ranged in size from 1 mm-72 cm (.04 in-28 in) and exhibited so much variation that they are classified into nine (or possibly ten) orders with more than 15,000 species. The smallest species are presumed to have been part of the free-floating plankton, while the more common, mid-sized species probably walked along the sea floor filtering mud to obtain food, and the larger varieties may have been swimming predators.