Five Classes of Echinoderms

Mnemonic Device:

• All Have Calcareous Ossicle Endoskeleton

Explanation: to remember that, other than tetra radial symmetry, the calcareous ossicle endoskeleton is the only characteristic shared by all 5 classes of this Phylum.

• Asteroidea (All)
• Holothuroidea (Have)
• Crinoidea (Calcareous)
• Ophiuroidea (Ossicle)
• Echinoidea (Endoskeleton)