Diagnosis
Carapace generally with well-developed rostrum, and in some species is strongly ornamented with sculpturing. First antenna is similarly developed in the two sexes and has a large seta on the dorsal surface of the second podomere, and terminates in 6 subequal setae. The endopodite of the second antenna has no processus mamilllaris, and in the male there is a hook appendage on both limbs. There is no sexual dimorphism of the fifth and sixth limbs. The caudal furca generally has 7-8 pairs of spine claws and a small dorsal seta, but in a few species there are only 5 pairs.
Genera
One known genus, Archiconchoecia (17 spp, 7 known from UK waters). Future taxonomic revision will probably lead to it being divided into at least three genera.