Dana, 1849
Females
Ce and Pd1 may be fused or separate, Pd4 and 5 always separate. R of 2 filaments. CR with 4 subequal, terminal setae and 1 outer seta. Ur of 4 somites. A1 25-segmented, generally segments 8-9 partly fused; segments 23 and 24 with elongate seta. A2 Coxa with 1 seta, Basis with 2 setae; A2 Exp 7-segmented; Exp1 and Exp2 with 2 setae each, Exp3-6 with 1 seta each, Exp7 usually with 1 seta nearly at midlength and 3 terminal setae; Enp1 with 2 setae, Enp2 with 14-16 setae. Mdp Basis with 4 setae; Enp1 with 4 setae and prominent lobe; Enp2 totally with 10-11 (8 or 9 terminal and 2 posterior) setae. Exp and Enp of approximately equal length. Mx1 Li1 with 9 terminal spines, 4 posterior and 1 anterior setae; Li2 and Li3 with 4 setae each; Li4 with 4 setae, Enp with 14-15 setae; Exp with 11 setae; Le1 with 9 setae; Le 2 with 1 seta. Mx2 Li1-Li5 with 4-6, 3, 3, 3 and 4 setae, respectively. Terminal part with about 10 setae. Mxp Coxa with 1 proximal seta, then with groups of 2, 4 and 4 setae from proximal to distal; Enp1-5 with 4, 4, 3/4, 4, 4/5 setae respectively. P2-P3 Basis with an external articulated spine, on P4 and P5 this may be reduced to a small seta. P2 Exp1 sometimes with recurved spine (Neocalanus), or Exp2 with deep invagination (Undinula).
Spine and seta formula: Spine and seta Calanidae.
P5 similar to P2-4; coxa sometimes with inner edge teeth (Calanus, Nannocalanus, Cosmocalanus).
Males
Ur of 5 somites. A1 25-segmented, with segments 1 and 2 always fused, segments 3-5, 7 and 8, 9 and 10, and 24 and 25 may also be fused. A2-Mx2 - either exactly as in female, or reduced in size and setation. Mxp with reduced inner setae but enlarged outer setae on terminal segments. P1-P4 as in female. P5 with both rami usually 3-segmented, right leg similar to other P, left leg variously modified; Enp sometimes reduced and devoid of segmentation on one or both sides.
There are now 8 genera in the family, all of which are found in the South Atlantic:
Genus Calanoides Brady, 1883
Genus Calanus Leach, 1816
Genus Cosmocalanus Bradford and Jillett, 1974
Genus Canthocalanus A. Scott, 1909
Genus Mesocalanus Bradford and Jillett, 1974
Genus Nannocalanus Sars, 1925
Genus Neocalanus Sars, 1925
Genus Undinula A. Scott, 1909