Baird, 1850
Diagnosis
This family contains two subfamilies the Cypridininae and the Azygocyprininae. The carapace ranges in length form 1 to 32 mm. The surface is usually smooth but is ornate in some species. The posterior end can be rounded or with a caudal process or siphon. There is always a rostral incisure present. The first antenna as two well developed setae on the eighth segment and in males there are suctorial discs on two if the setae. The exopodite of the second antennae is similar in the two sexes, and in the females the endopodite consists of 1 to 3 segments. The seventh limb is well developed and shows considerable variation in the numbers of setae and the types of end combs. The frontal organ is generally short and bulbous or peg-like, but it is never elongate as in most species of the other families. Each lamella of the caudal furca carries between 4 and 28 claws. The lateral eye is well developed with many ommatidia in shallow-living species. The naupliar eye is usually large and well pigmented.
Remarks
This family includes around 25 genera, and includes species from nearly all marine habitats, from all depths and most latitudes. However, they are most diverse in shallow low latitude seas. There are a relatively few planktonic species that occur in the deep ocean.
[Adapted from Angel, 2000]