Giesbrecht, 1892
Females
Body elongate, especially anterior to A2, more or less transparent, often with triangular anterior part of Ce. Ce and Pd1 fused, Pd4 and 5 partly fused.CR sometimes asymmetrical; usually left ramus slightly and second seta much longer than others. R of 2 long, slender filaments. Ur of 3 or 4 somites with CR usually completely fused to anal somite. A1 23-segmented, generally with segments 1-2 and 8-9 fused. A2 Exp shorter than Enp; Exp1 and Exp2 with 2 setae each, and either fused or separate.
Md Enp reduced and Basis and Exp elongate (except in Rhincalanus). Mx1 Li1 with 14 terminal spines and setae including 4 posterior and 1 anterior setae; Li2 may be absent or without setae, Basis and Enp elongate; Exp with reduced number of setae; Le2 with 1 seta; Le1 with 9 setae. Mx2 Li1-Li5 with 6, 3, 3, 3 and 3-4 setae, respectively. Mxp Enp1-Enp5 with 3, 4, 3, 4 and 4 setae respectively. Terminal Exp spines of swimming legs smooth.
Spine and seta formula: Spine and seta Eucalanidae.
P5 absent (Eucalanus, Pareucalanus, Subeucalanus), or present, 3-segmented, symmetrical.
Males
Ur of 5 somites, with CR usually completely fused to anal somite. A1 24-segmented. Oral parts and P similar to females. P5 uniramous on both sides (Eucalanus, Pareucalanus), biramous on left (Rhincalanus), or absent on right (Subeucalanus).
The family includes the following genera, which are all found in the South Atlantic:
Genus Eucalanus Dana, 1852
Genus Pareucalanus Geletin, 1976
Genus Rhincalanus Dana, 1852
Genus Subeucalanus Geletin, 1976