Ostracoda

Ostracoda is a class of the Crustacea commonly called seed shrimp, comprising about 33000 described species across seven valid orders. Most are tiny, typically around a millimeter long though ranging from 0.2 to 32 millimeters, and their bodies are usually enclosed in a bivalve like shell of chitin and often calcium carbonate; feeding habits vary widely, though deposit feeding is the most common strategy, and molecular studies have not yet confirmed whether the class is a single natural lineage.