Answer:
The starfish is an echinoderm, this group is closely related to sand dollars, and feather stars. The echinoderms don’t have a notochord, and they are not closely related to chordates, they have no backbone like all invertebrates, they have external skeletons of calcareous plates. They are multicellular and all the cells have different responsibilities to keep the animal alive.
For all this characters they fits into the cladogram of invertebrates.
