Type: Archidiaptomus arrorus Madhupratap & Haridas, 1978. Total : 1 sp.
Brackish water on the coast of India.
After Madhupratap & Haridas (1978, p.257) this genus and species possesses many 'primitive' characters and strong affinities to the family Diaptomidae. The 2-segmented exopod of the P5 female (though somewhat peculiar in form) is typical of the Pseudodiaptomidae; but it is unique in maintaining fully developed endopods of an unusually spinous form. This appears to be a primitive or generalised condition placing this genus very close to the Diaptomidae. The exopods of the right and left P5 male are fully developed as in the Pseudodiaptomidae (in the Diaptomidae the left one is usually smaller). But it is again unusual in maintaining the primitive feature of both endopods being fully developed whereas in Pseudodiaptomus the endopods of the P5 male are either rudimentary or lacking. The urosome is 4-segmented in the female (3-segmented in the Diaptomidae) and 5-segmented in the male as in the Pseudodiaptomidae and the ornamentation of the genital segment is also somewhat pseudodiaptomid in character. The A1 has a greater number of segments than the species of thje genus Pseudodiaptomus (mostly 20 to 22, 23 in some) and in having 24 segments approaches the 25-segmented nature of the diaptomid A1, which is considered as a primitive condition in calanoid Copepoda. The right geniculate A1 of the male has 4 terminal segments as is usually found in the Diaptomidae (2 to 3 in the Pseudodiaptomidae). The P1 has a 3-segmented endopod typical of the Pseudodiaptomidae as against the 2-segmented condition in the Diaptomidae; while the unarmed nature of the outer margin of the 2nd exopodal segment of P1 is a feature shared by the species of both families, the rounded form ofv the posterior angles of the metasome and the long caudal rami of the present type-species are pseudodiaptomid characters.

Definition from Bradford-Grieve (1999 b, p.148) :
- As for the family definition.
- Head and pedigerous segments 1 and 2 fused, pedigerous segments 4 and 5 fused.
- Female urosome 4-segmented.
- Female genital segment symmetrical, with small anterolateral swellings, decorated with spinules.
- A1 24-segmented.
- P1 exopodal segment 3 without outer edge spines, endopodal segment 3 with 6 setae.
- Female P5 biramous, symmetical; endopod 1-segmented with a terminal claw-like process at the tip; exopodal segment 1 with 1 single long outer spine, exopodal segment 2 with 4 spines, terminal one the longest.
- Male P5 biramous, asymmetrical; endopods on both sides extending to middle of exopodal segment 2; left exopodal segment 1 with 1 outer distal spine and 1 longer curved inner spine, exopodal segment 2 with 1 long proximal spine and the segment terminates in 2 claw-like spines; right leg exopodal segment 2 with 1 inner spinule and 1 outer spine, segmentation between exopodal segments 2 and 3 indistinct, the latter forms a long spine with a proximal inner spinule.

Type: Calanipeda aquaedulcis Krichagin, 1873. Total: 1 sp.
Euryhaline, in estuaries around the Mediterranean, Black Sea and in the Caspian Sea.

Definition from Bradford-Gieve (1999 b, p.148) :
- As for the family definition with the following additional characters after Dussart (1967).
- Head and pedigerous segment 1 separate, pedigerous segments 4 and 5 fused.
- Posterior border of prosome rounded.
Urosome 4-segmented in female.
- Urosome male 5-segmented.
- Caudal rami 6-7 times as long as wide, inner edges hairy, with 5 well-developed setae.
Female genital segment swollen anteriorly with left side extended into a curved hook directed posteriorly and carrying a sensory spine.
- A1 25-segmented, segment 25 very small extending to posterior border of urosomal segment 2.
- Exopod of A2 6-segmented.
- Male A1 prehensile on right without either a hook nor hyaline lamella on three last segments.
- P1 to P4 with 3-segmented exopods and endopods.
- Female P5 slightly asymmetrical, without endopods; exopod 3-segmented, exopodal segment 2 with 1 strong inner spine, a strong, distal, spiniform extension, and at its base 1 small strong spine; exopodal segment 3 in the form of a powerful hook, curved inwards with 1 strong internal spine and a small spinifotm extension at its base.
- Male P5 basipod 2 large on right with 1 short seta at postero-internal angle; exopod 3-segmented, exopodal segment 1 slightly elongate with a moderate spine on postero-external angle; the two last segments of exopod form a powerfull hook; exopodal segment 2 strongly curved towards exterior and with a long extension and with 1 short slender marginal seta at midlength; exopodal segment 3 thin, long, and pointed terminally with 1 fine seta on its external border; endopod 1-segmented extending to distal border of exopodal segment 1 and armed with small spines and some terminal hairs. Left leg much shorter than right; exopod 2-segmented ; exopodal segment 1 with an elongate spiniform extension at antero-external angle reaching the distal end of exopodal segment 2 which is large, conical, and terminated by 2 subequal points; endopod 1-segmented, enlarged distally, reaching the base of exopodal segment 2, carrying at its extremity small unequal spines.

Vyshkvartzeva (1980: pers. comm.) draws attention to the fact that considering the genus Mazellina as a synonym of Pseudodiaptomus is an opinion which does not carry away conviction. For Vervoort (1965, p.97) there is no doubt on the identity of the two genera (M. galletti seems very close to P. dauglishi). Type: Pseudodiaptomus pelagicus Herrick, 1884. Coastal forms, brackish, freshwater; epibenthic in daytime. Total: 80 spp. + 2 varieties + 2 unident.
According to Walter & al., 2006 (p.203, 213, Table 2) among the 77 currently recognized species, the mouthparts and swimming legs are almost identical in shape, segmentation, spination, and/or spinulation patterns. The female genital double-somite is of particular interest (Soh & al, 2001; Walter & al., 2002 [see also Barthélémy, 1999 a]) especially regarding the ventral genital flaps and egg sac number. A1 segmentation has 3 basic patterns within this genus. The P5 females is typically symmetrical and of limited value to separate the species; the male P5 typically provides the most reliable morphological characters used for species determination and species group placement, notably the presence and /or absence of the left and /or right endopods easily indicates to which group a species belongs.

Definition from Bradford-Grieve (1999 b, p.149) :
- As in the family definition.
- Head and pedigerous segment 1 fused or separate, pedigerous segments 4 and 5 fused.
- Posterior prosomal corners often extended into points.
- Female urosome 2-4-segmented.
- Female genital segment variously ornamented, may be asymmetrical.
- Female P5 uniramous with 3-segmented exopods; in posterior view - basipod 2 with 1 large and 1 small surface seta; exopod segment 1 with a distal outer spine and 2 surface setae; exopod segment 2 with 1medial setz produced into a spiniform process which is plumose or spinulose along both margins, and 1 outer small naked ot plumose spine; exopod segment 3 spiniform, distally produced, usually equal in length or longer than exopod segment 2 spiniform process, with both margins hairy, also with a proximomedial spiniform process.
- Male P5 uniramous or biramous. Posterior view - right leg basipod 1 with a subapical spinule row; basipod 2with 1 large plumose seta and at least 1 small surface seta; exopod segments 1-3 each with at least 1 small surface seta,exopod segment 1 with 1 outer spine, exopod segment 3 proximally thickened with a medial basal swelling or process, concavely produced, and distal half of medial margin hairy, with 1-2 setae; left leg basipods 1 and 2 as on right leg; with or without an endopod; exopod segment 1 with at least 1 surface seta and variably shaped; exopod segment 2 with several surface setae, outer spine near midlength, and typically with 1 terminal spine; in anterior view: right leg basipod 1 with a hair or spinule row; basipod 2 possesses lateral spinule row that continues onto surface at midlength, and usually with an endopod; exopod segment 2 with variably shaped outer spine; left leg basipods 1 and 2 ornamented as on the right.