All the planktonic ostracods belong to the subclass Myodocopa, and most belong to the order Halocyprida, which lack obvious eyes. A few belong to the order Myodocopida Sars, 1866, which either have lateral compound eyes (Macrocypridina) or large central naupliar eyes with parabolic reflectors (Gigantocypris).
The full taxonomic hierarchy of the planktonic species Conchoecia magna.
All the ostracods have the body totally enclosed within their carapace (or shell). Adults typically have seven pairs of limbs, but the full set of limbs is only developed fully in adults. Juvenile instars have either fewer or only partially developed limbs.
The myodocopids have distinctive characteristics; the description that follows is for a typical halocyprid species.