Sars, 1902
Females
Ce and Pd1 usually fused, or separated, Pd4 and 5 fused completely, or incompletely. R present, of 2 filaments (Xanthocalanus, Brachycalanus), or 2-pointed (Phaenna), or as a bifurcated plate with slight (Neoscolecithrix), or strong (Cornucalanus, Onchocalanus) bifurcation. Posterior corners of Pr and Gns symmetrical. Posterior corners of Pr extended into 2 points each (Neoscolecithrix), prolonged into lobes (Xanthocalanus), or not prolonged into lobes, rounded or triangular.Ur of 4 somites. A1 21-25-segmented, 8-9 segments fused. A2 Exp nearly equal or longer than Enp, 6-segmented; Exp 1 without setae, Exp 2 without medial setae (in Neoscolecithrix Exp1-Exp2 with 2 setae each). Mdp Basis usually with 3 setae. Mx1 Li1 usually with 8-9 terminal and 4 posterior setae (Xanthocalanus, Cephalophanes, Neoscolecithrix), 7 terminal and 3 posterior setae (Brachycalanus), or only 9 terminal setae in Phaenna; and with total number of 10-12 setae in Cornucalanus and Onchocalanus; Li2 usually with 2 setae, sometimes with 1 seta (Phaenna), 3 setae (Neoscolecithrix, some species of Xanthocalanus), or 4-5 setae (some species of Xanthocalanus, Talacalanus); Li3 with 3-4 setae; Li4 usually with 5 setae, rarely with fewer setae (3 setae in Phaenna); Enp has from 6 (Phaenna) up to 13 setae (Brachycalanus); Exp usually with 10 setae (in Phaenna 5 setae ); Le1 with 9 setae. Mx2 Li1-Li5 with 5 (rarely 4), 3 , 3 (2 in Phaenna), 3 (2 in Phaenna) and 4 setae respectively; one seta of Li5 may be transformed into sensory worm-like appendage (Phaenna, some species of Brachycalanus, Xanthocalanus harpagatus, in latter species one of setae on Li3 also worm-like); Li5 has strong claw-like spine in Cornucalanus and Onchocalanus; terminal part of limb usually with 1 worm-like and 7 brush-like sensory setae (in some species of Xanthocalanus and Brachycalanus 2 worm-like appendages and 6 brush-like appendages have been recorded), rarely number of brush-like appendages greater (8 in Brachycalanus bjornbergae); number and composition of sensory appendages in Neoscolecithrix differs (3 worm-like and 4-5 brush-like), similar to that of scolecitrichids. Mxp Coxa with 1 proximal seta, then with 2 (rarely 1) setae, 2 setae (usually 1 brush-like and 1 sclerotized seta) and 3 setae from proximal to distal; in Neoscolecithrix setal composition differs: 1 proximal seta, then 2 setae (1 worm-like and 1 sclerotized), 2 setae (1 brush-like and 2 sclerotized) and 3 setae from proximal to distal; Enp1-Enp5 usually with 4, 4, 2-4, 3-4 and 4 setae; sometimes Enp2-3 each with strong, spine-like attenuations (Cornucalanus). P1 Enp with well developed external lobe. P2-P4 wide and flat, surfaces may be covered by spines and spinules, sometimes strongly (Brachycalanus).
Spine and seta formula: Spine and seta Phaennidae.
P5 usually 3-segmented, sometimes 2-segmented (Xanthocalanus in part), or absent (Phaenna).
Males
R similar to that of females. Oral parts reduced compared with those of female. P5 uniramous, legs almost equal in length, left leg 5-segmented, slightly longer than 4-segmented right leg (Phaenna), or strongly asymmetrical, unequal in length, with long 5-segmented left leg, and short 3- or 4-segmented right leg; sometimes right P5 5-segmented and very short, reaching only first segment of left leg (Xanthocalanus).
There are six genera in Phaennidae, all but Cephalophanes known from the South Atlantic:
Genus Brachycalanus Farran, 1905
Genus Cephalophanes Sars, 1907
Genus Cornucalanus Wolfenden, 1905
Genus Onchocalanus Sars, 1905
Genus Phaenna Claus, 1863
Genus Xanthocalanus Giesbrecht, 1892
The genus Neoscolecithrix Canu, 1896 is of unclear taxonomic status (see Schulz and Beckman, 1995) and is placed conventionally here in the Phaennidae. Talacalanus Wolfenden, 1911 has been redefined by Campaner (1978b) to accomodate Xanthocalanus greeni Farran, 1905, and Xanthocalanus maximus Brodsky, 1950, but this genus seems very close if not identical to Xanthocalanus.
Representatives of all genera except Cephalophanes have been taken in the South Atlantic.