Southern Australia A feature that distinguishes an ostracod from other crustaceans is the carapace that enloses the body. Because the legs are hidden they may at first be confused with small bivalve molluscs. Don't be deceived by their external simplicity however because the carapace packs a lot in. There are several pairs of short limbs which enable the animal to scramble around and feed on the floor of the sea. Some are able to swim and rare examples are terrestrial in damp places in Australian forests.
Geologists rely on the fossilized carapaces of ostracods to date sediments.
Ostracods are often overlooked because they are so small but can be very common. In Australia there are hundreds of species, many undescribed. Identification of species or even families demands exceptional dissection skills and a very good microscope.