Members of the Branchiopoda are unified by the presence of
gills on many of the animals'
appendages, including some of the
mouthparts. This is also responsible for the name of the group
 (from the
Greek: branchia, gills, akin to bronchos,
Greek: pous, foot).
 They generally possess
compound eyes and a
carapace, which may be a shell of two valves enclosing the trunk (as in most Cladocera), broad and shallow (as in the Notostraca), or entirely absent (as in the Anostraca).
 In the groups where the carapace prevents the use of the trunk limbs for swimming (Cladocera, clam shrimp and the extinct
antennae are used for locomotion, as they are in the
 Male fairy shrimp have an enlarged pair of antennae with which they grasp the female during mating, while the
bottom-feeding Notostraca, the antennae are reduced to
 The trunk limbs are beaten in a
metachronal rhythm, causing a flow of water along the midline of the animal, from which it derives
food and, in the case of the Anostraca and Notostraca, movement.