Sea stars (starfish) are part of the forcipulatida order of marine animals because they possess certain traits peculiar to this order. According to the Marine Species Identification Portal website, these include "starfish with generally inconspicuous marginal plates" and with dorsal spines that could be single or grouped. The tube feet do not have sucking discs and they have crossed and straight pedicellariae, a small type of forceps-like claw.
All types of sea stars of the forcipulatida order have certain characteristics in common. They do not possess backbones but instead have hard, bony plates underneath the skin. They have spines that cover the dorsal or top part of their bodies; their tube feet are used to move the creature as well as for feeding. And it can expel its stomach out through its mouth, which is under its body. The stomach then absorbs and starts digesting the prey.
Sea stars of the forcipulatida order can regrow limbs and/or new sea stars from the broken limb. They have a crude nervous system. They reproduce by dividing themselves into two. They also have chemicals beneath their skin that they can eject as defense mechanisms when they are faced with enemies.
Although sea stars have a system of nerves, they do not possess a brain. However, they "learn" through conditioning or experiences. They do not live in families but do join together in swarms during certain times such as when they are spawning, feeding or migrating. They also respond to variations in light or when there is a high or low tide. These periods correspond with good feeding opportunities.