The Echinoid Directory

Characters supporting cladogram:-

1. More than one pore and tube-foot associated with each ambulacral plate outside petals.

2. Sphaeridia enclosed within ambulacral plates, not in open pits. Ambulacral pores and tube-feet along horizontal sutures and/or lie scattered in bands within plate not simply forming a vertical adradial band.

3. Petals composed of alternating primary and demi-plates. Interambulacral zones always disjunct adorally.

4. Perignathic girdle composed of five interradial muscle-attachment pegs.

5. Interambulacral zones terminate adapically in one or more single plates.