Aboral madreoporite
Oral surface faces substrate
Common name: Sand dollar
Common name: sea lilies
Arms widely connected to calyx
Common name: Sea Urchin
Common name: brittle stars
Arms narrowly connected to calyx
Endoskeletal plates of CaCO3
External ciliary grooves
Ambulacral grooves extend aborally
Endoskeletal plates fused as test
Class Ophiuroidea + Class Echinoidea + Class Holothuroidea
Endoskeletal plates reduced
Common name: sea cucumbers
Ambulacral grooves
Ambulacral grooves closed
Sister classes
Pentaradial symmetry
Stalked
Water vascular system
Common name: sea stars
