Echinoderm is an invertebrate animal that belongs to the phylum Echinodermata. It includes species such as STARFISH, URCHIN, and crinoid. STARFISH is an eight-letter word for a type of echinoderm that has a star-shaped body with five or more arms. URCHIN is a six-letter word for a type of echinoderm that has a spiny, globular body. Crinoid is a seven-letter word for a type of echinoderm that has a stem and feathery arms. All three types of echinoderms have a water vascular system and a calcium carbonate endoskeleton.