Sewell, 1947
Females
Ce and Pd1 may be fused or separate. Pd4 and 5 separate. Ur of 4 somites. R with 2 thick sausage-like appendages, or 2 sharp slightly tapering spines, or filaments which narrow terminally. A1 25-segmented, 8-9 segments partly fused (here and below only free A1 segments are mentioned). A2 Exp 7-segmented; Exp1 with 1 seta or without setae; Exp2 with 3 with or without setae. Mdp Exp and Enp well developed, Basis with 4 setae, Enp1 with 4 setae and internal lobe-like projection (may be absent), Enp2 with 9 terminal and 2 posterior setae. Mx1 Li1 with 9 marginal spines, 1 anterior and 4 posterior setae (Megacalanus), or 12-13 setal elements (Bathycalanus, Bradycalanus); Li2 with 4 setae (setae absent in Bathycalanus); Li3 with 2 (Bathycalanus, Bradycalanus), or 4 setae (Megacalanus); Li4 with 2 to 4 setae; Enp1 with 3 setae (or with 1-2 setae in Bathycalanus and Bradycalanus), Enp2 with 4 setae, and Enp3 with 7 setae (Enp2 with 1 and Enp3 with 4-6 setae in Bathycalanus, Bradycalanus); Exp with 11 setae; Le2 with 1 seta; Le1 with 9 setae. Mx2 Li1-Li5 with 5-6, 3, 3, 3, and 3-4 setae, respectively; terminal setae may be very long, curved at tips looking like ribbon-like lamella (Bathycalanus); outer seta on coxa present. Mxp Coxa with 1 proximal seta, then with groups of 2, 4 and 3-4 setae from proximal to distal; Enp1-Enp5 with 4, 4, 3, 4 and 4 setae respectively (except in Bathycalanus). P1 Exp3 with 1 external spine in Bathycalanus richardi. P2-P3 Basis with articulated external spine.
Spine and seta formula: Spine and seta Megacalanidae.
P5 similar to P2-4.
Males
Ur of 5 somites. A1 25-segmented, segments 7-9 may be fused. Right A1 is geniculated in Bathycalanus. A2-Mx2 similar to that of female. P1-P4 as in female. P5 with 3-segmented rami similar to female P5; Enp1 without inner setae; Exp3 with different armament, also left Exp2 with inner distal projection, or seta.
The family includes 3 genera, all are found in the South Atlantic:
Genus Megacalanus Wolfenden, 1904
Genus Bathycalanus Sars, 1905
Genus Bradycalanus A. Scott, 1909