The oceans of the Early Paleozoic contained a wide variety of organisms. Scientists know about these organisms from the fossil record and infer their behavior from modern species. All arthropods are similar in that they have an exoskeleton, paired, jointed appendages and a segmented body. Trilobites were motile, epifaunal organisms believed to be scavengers. They occupied two ecological zones, deep ocean and shallow shelf.
Trilobites are important guide fossils because their morphology changed frequently.
Some obtained lengths of 3 meters. They were sessile, infaunal filter feeders. 120 species still exist today. A conical shaped sessile, epifaunal filter feeder. Abundant in the Early Paleozoic, extinct by Permian.