Ostracods, or ostracodes, are a
class of the
Crustacea (class
Ostracoda), sometimes known as
seed shrimp. Some 70,000 species (only 13,000 of which are
extant) have been identified, grouped into several orders. They are small crustaceans, typically around in size, but varying from in the case of
Gigantocypris. Their bodies are flattened from side to side and protected by a
bivalve-like,
chitinous or calcareous valve or "shell". The hinge of the two valves is in the upper (dorsal) region of the body. Ostracods are grouped together based on gross morphology, but the group may not be
monophyletic; their
molecular phylogeny remains ambiguous.
