Sars, 1902
Females
Small copepods with one median eye; no rostrum; a semicircular plate, thickly covered with short bristles, lies before the labrum. Ce and Pd1 separate; Pd4 and 5 fused or separate, posterior corners of Pd5 with rounded or pointed projections which are often asymmetrical. Ur of 2-3 somites; Gns often asymmetrical, bearing common genital aperture located medially on the ventral surface, copulatory pore contained within median genital aperture. CR sometimes asymmetrical, one larger than other, often fused to anal somite, with 6 setae. A1 12- to 15-segmented with proximal segments fused. A2 Coxa and Basis separate, Enp and Basis often fused; with Exp indistinctly 3-segmented, typically with segment 1 unarmed, long middle segment with up to 3 setae, and short apical segment with 2 setae; Enp 2-segmented with 6 terminal setae. Md with elongate palp; unarmed Basis; Enp 2-segmented with 0 and 6 setae; Exp indistinctly 1-4-segmented with 5 setae in total. Mx1 with very much reduced number of lobes (Li1 and distal segment present); Li1 with up to 13 spines and setae, distal segment elongate bearing 3 powerful claw-like setae around apex, and may have up to 7 spines subapically. Mx2 with Li1-4 reduced, Li5 with 3 setae, 2 of them claw-like; Enp with 6 claw-like setae plus 1 or 2 smaller setae. Mxp reduced, with 2-5 long spinulate setae on first segment; the distal part of limb 2-segmented, bearing 3 or 4 setae on inner margin and 1 on outer margin of distal segment. Swimming legs with 3-segmented Exp; Enp of P1 2-3-segmented, P2-4 2-segmented.
Female P5 not natatory, uniramous, 2-3-segmented; Coxa and intercoxal plate fused; Basis with outer seta; 1 free Exp segment present, sometimes in form of curved tapering process, typically with 1 outer margin spine and 3 spinous processes arranged along margins.
Males
Posterior corners of Pd5 with small rounded or pointed extremities or without protrusions. Ur of 5 somites, often asymmetrical; genital aperture located ventrolaterally on left posterior border of Gns, Ur2 sometimes with posterolateral process. Right A1 prehensile, its middle part widened and sometimes equipped with denticulate plate. P5 asymmetrical, uniramous; 3-segmented on right, segment 1 unarmed, segment 2 often expanded into medial or distal lamellate process armed with up to 3 setae, segment 3 forming subchela typically curved and armed with 3 or 4 small setae. Left P5 4-segmented; segment 1 unarmed, segments 2 and 3 elongate each with inner and outer seta, segment 4 curved, typically armed with 2 setae on inner margin, 1 apical seta and 2 setae on outer margin; inner seta on segment 3 often carried on slender process. Eggs probably released into water.
This family is monotypic. Tortanus has been reviewed (Ohtsuka, 1992) and has been divided into the subgenera Tortanus Giesbrecht, 1898; Eutortanus Smirnov, 1935; Acutanus Ohtsuka, 1992; and Atortus Ohtsuka, 1992. Only one species, Tortanus (Tortanus) gracilis (Brady, 1883), has been taken in the South Atlantic.