[5] Five long, segmented arms at least eight times the diameter of the disc extend from the body which are covered in flattened spines [6] and tube feet.

[7] Their central nervous system is highly metameric with the same pattern of peripheral nerves repeated in each arm.

[8] Instead of using their tube feet for locomotion, Amphiodia occidentalis and several other brittle star species use their arms to crawl along the substrate.

In both techniques, the designated right and left forelimbs are highly synchronized while the hind limbs present greater variability.

[7] Amphiodia occidentalis has separate sexes and are broadcast spawners,[10] releasing their eggs and sperm into the water column where fertilization and larval development occurs as plankton [11] Their breeding cycles are periodic with higher rates of spawning activity in the winter and spring.