Giesbrecht, 1892
Females
Ce and Pd1 usually fused. Pd4 and 5 fused, or separated. Ur of 2 to 4 somites. Anal somite usually longer than any somite between it and Gns. R of 2 filaments (Acrocalanus, Calocalanus, Paracalanus); 2-pointed, solid (Delius, Bestiolina); or massive (Parvocalanus). A1 usually 25-segmented, generally with segments 1 and 2, also 8 and 9, partially fused; in Delius first 8 segments fused. A2 Exp 7-segmented with Exp1 and Exp2 each bearing 2 setae, segment 7 elongate. Md Enp1 without prominent lobe. Mx1 Li1 with 14 setal elements (4 posterior and 1 anterior setae, and 9 terminal spines); Li2 and Li3 with 3-4 setae each; Li4 with 4 setae; Enp with 13-14 setae; Exp with 11 setae; Le2 with 1 reduced seta; Le1 with 7-9 setae. Mx2 Li1-Li5 with 6, 3, 3, 3 and 3-4 setae respectively; terminal part with 8 setae, 1 of them may belong to developed Li6. Mxp Coxa with 1 proximal seta, then 3 groups of 2, 3 and 4 setae from proximal to distal; Enp1-Enp5 with 3, 4, 3, 3+1 and 4 setae respectively. P1-P4 Exp usually 3-segmented but P1 Exp 2-segmented in some Calocalanus species. P2-P4 Enp usually 3-segmented but 2-segmented in Calocalanus minor, posterior surfaces of some segments ornamented with spines. P2-P4 Exp3 external borders serrated, or smooth in Delius and Calocalanus). Terminal spines of P2-P4 Exp smooth.
Spine and seta formula: Spine and seta Paracalanidae.
P5 uniramous, absent, or vestigial (Acrocalanus), present on left only (Delius). If both P5 present, then symmetrical, presented by coxae (Bestiolina), 2-segmented (or 3-segmented) (Paracalanus, Parvocalanus), or 3-4 segmented (Calocalanus).
Males
Ur of 5 somites. Genital opening on left (in Calocalanus on left or right). Cephalic hump present (Acrocalanus, Bestiolina and Paracalanus), or absent. A1 25 segmented, with some or all of segments 1-6 fused and swollen, segments 9-10 may also be fused. A2 Exp 7 very short without 3 terminal setae which are present in female. Exp1 and Exp 2 without setae. Other oral parts reduced compared with female. Right P5 may be absent (Acrocalanus, Delius), or present as Coxa (Bestiolina), 2-3-segmented (Paracalanus, Parvocalanus), or 3-4-segmented (Calocalanus).
The family includes the genera:
Genus Acrocalanus Giesbrecht, 1888
Genus Bestiolina Andronov, 1991
Genus Calocalanus Giesbrecht, 1888
Genus Delius Andronov, 1972
Genus Paracalanus Boeck, 1864
Genus Parvocalanus Andronov, 1970.
Of these, only Bestiolina has not been recorded in the South Atlantic.