[2] 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).

[3] In the groups where the carapace prevents the use of the trunk limbs for swimming (Cladocera and clam shrimp), the antennae are used for locomotion, as they are in the nauplius.

[3] The trunk limbs are beaten in a metachronal rhythm, causing a flow of water along the midline of the animal, from which it derives oxygen, food and, in the case of the Anostraca and Notostraca, movement.

[3] But notostracans are omnivorous and very opportunistic feeders and will eat algae and bacteria in addition to animals as both predators and scavengers.

[13] Lipostraca contains a single extinct Early Devonian species, Lepidocaris rhyniensis,[14] which is the most abundant animal in the Rhynie chert deposits.

[19] The two genera, Triops and Lepidurus, are considered living fossils, having not changed significantly in outward form since the Triassic.

[3] Phenotypic plasticity within taxa makes species-level identification difficult, and is further compounded by variation in the mode of reproduction.

[21] Notostracans are the largest branchiopodans and are omnivores living on the bottom of temporary pools, ponds[21] and shallow lakes.

[24] In the water bodies of the world, a lot of Cladocera are non-native species, many of which pose a great threat to aquatic ecosystems.

[26] It is thought that the group evolved in the seas, but was forced into temporary pools and hypersaline lakes by the evolution of bony fishes.