- The animals of phylum echinodermata have an endoskeleton of calcareous ossicles and, hence, the name Echinodermata.
- All are marine with organ-system level of organization, the adult echinoderms are radially symmetrical but larvae are bilaterally symmetrical, triploblastic and coelomate animals.
- Digestive system is complete, excretory system is absent.
- Water vascular system, the most distinctive feature, helps in locomotion, capture and transport of food and respiration.
- Sexes are separate, reproduction is sexual, fertilisation is usually external and development is indirect with free-swimming larva.
Examples-Asterias (Star fish), Echinus (Sea urchin).
Fig. Star fish