Sea stars
Sea stars are star shaped marine invertebrates. Lower classifications of sea stars include Brisingida, Velatida, Spinulosida. The surface of the sea stars, or aboral, can be smooth, granular or spiny, and is covered with overlapping plates. The first record of a sea star of is 450 million years old. Current day sea stars are gonochorous meaning there are both male and female sea stars.Sea stars do have a nervous system, while they lack a centralized brain they do have a complex nervous system. It has a nerve ring around the mouth and a radial nerve running along the ambulacral region. The peripheral nerve system consists of two nerve nets: a sensory system and a motor system but sea stars do not have the ability to control their actions.