Phylum Echinodermata - (Spiny Skinned Animals)
They are exclusively marine organisms and the adults are radially symmetrical, but the larvae remain bilaterally symmetrical. They have an exoskeleton with calcareous ossicles, presence of external spines called Pedicellaria. The mouth is on the lower surface. Water vascular system is a unique feature of these animals. Tube feet is involved in locomotion. The most common larva is a bipinnaria larva.