Marine invertebrates of the Ophiuroidea (phylum Echinodermata). They have long thin arms which set from a small disc shaped body.

Brittle stars are echinoderms, closely related to starfish. They crawl across the sea-floor using their flexible arms as "legs" for locomotion. The ophiuroids generally have five long slender, whip-like arms which may reach up to 60 centimeters (2 feet) in length on the largest specimens.