Type: Corynura gracilis Brady, 1883. 5 S.G.: Acutanus , Atortus, Boreotortanus, Eutortanus , Tortanus . Total: 47 spp. + 1 undet.

Diagnosis from Bradford-Grieve (1999 b, p.228):
- 1 median eye.
- No rostrum; a semicircular plate, thickly covered with short bristles, lies anterior to the labrum.
- Head and pediger segment 1 separate, pediger segments 4 and 5 fused or separate.
- Posterior corners of pediger segment 5 with rounded or pointed extremities which are small or absent in the male.
- Urosomal segments 2- or 3-segmented in female
- Genital segment female without seminal receptacles.
- Urosome 5-segmented in male, often asymmetrical, both because of asymmetry in individual segments and as a result of curvature along the longitudinal axis; urosome asymmetry less frequent in males.
- Female genital segment often asymmetrical, bearing a common genital aperture located medially on ventral surface, copulatory pore contained within median gemital aperture.
- Caudal rami sometimes asymmetrical, one larger than the other, often fused to the anal segmebt, with 6 setae.
- A1 12- to 15-segmented, prehensile on the right side in the male, its middle part widened and sometimes equipped with a denticulate plate.
- A2 coxa and basis separate, endopod and basis often fused; with exopod indistinctly 3-segmented, typically with an unarmed 1st segment, a long middle segment with up to 3 setae, and a short segment with 2 setae; endopod 2-segmented with 6 terminal setae.
- Md with an elongate palp; unarmed basis; endopod 2-segmented with 0 and 6 setae; exopod indistinctly 1- 4-segmented with 5 setae in total.
- Mx1 with much reduced number of lobes (inner lobe 1 one other the only ones present); inner lobe 1 with up to 13 spines and setae, the distal segment elongate bearing 3 powerful claw-like setae around the apex, and up to 7 short setae subapically.
- Mx2 with lobes 1-3 reduced; the remaining lobes bear claw-like setae.
- Mxp reduced with 2 long spines on the 1st segment; the distal part pof the limb bearing 3 or 4 setae on the inner margin and 1 on the outer margin of the distal segment.
- Swimming legs with3-segmented exopods; endopod of P1 2 or 3-segmented; P2-P4 with 2- segmented endopodss.
- Female P5 simple, uniramous, 2-3-segmented; coxa and coupler fused; basis with an outer seta; free exopodal segment typically with 1 outer margin spine and 3 spinous processes arranged around the margins; exopod segment sometimes in the form of a curved tapering process.
- Male P5 asymmetrical, uniramous; right leg 3-segmentd, 1st segment unarmed, 2nd segment often expanded into a medial or distal lamellate process armed with up to 3 setae, 3rd segment forming a subchela typically curved and armed with 3 or 4 small setae; left leg 4-segmented, 1st segment unarmed, 2nd and 3rd segments elongate, each with an inner and outer seta, 4th segment curved, typically armed with 2 setae on the inner margin, 1 apical seta and 2 on the outer margin; the inner seta on the 3rd segment often carried on a slender process.

Diagnosis from Mulyadi (2004, p.164):
- Cephalon without lateral hook.
- Rostrum absent, horse shoe-shaped plate fringe with hairs anterior to upper lip.
- Eye large, without lenses.
- Cephalon and pediger somite 1 separated, pediger somites 4 and 5 fused or separated.
- Corners of last thoracic somite pointed and sometimes asymmetrical in female, rounded in male.
- Urosome 2 or 3 somites and usually asymmetrical in female; 5 somites in male.
- Caudal rami usually very asymmetrical in female, less so in male.
- A1 17-segmented; male right A1 prehensile, thickened at middle.
- Endopod of A2 little longer than exopod.
- Basis of Md long; outermost tooth of gnathobase large and well separated from other teeth.
- Mx1 reduced to basal segment bearing short broad proximal lobe and long narrow distal lobe, the latter with 2 long and 1 shorter apical setae.
- Mx2 with much reduced proximal lobe.
- Mxp with well-developed basal segment armed with strong setae; endopod much reduced.
- P1-P4 with 3 exopodal segment, 2 or 3 endopodal segments in P1, 2 endopodal segments in P2-P4.
- P5 uniramous in both sexes, 2-3-segmented and sometimes asymmetrical in female; right P5 male forming a chela.

Key to subgenera from Ohtsuka & Reid (1998, p.775) :
1 – Right caudal ramus of female bearing large acute outer process ; right caudal seta II of male much thicker and longer than left ; 2 nd endopod segment of leg P4 bearing 7 setae …….. Tortanus (Boreotortanus) Ohtsuka & Reid, 1998.
1’ – Caudal rami of both sexes not as above ; 2 nd endopod segment of leg P4 with 6 setae ……… 2.
2 – Mxp syncoxa beraing 5 setae ……. 3.
2’ - Mxp syncoxa bearing only 2 setae …… 4.
3 – In both sexes, dorsal terminal triangular process present on both caudal rami ; prosomal corners of female not produced ; caudal rami of male exyremely slender, as long as or longer than urosomites compined, 2 nd endopod segments of legs P2 and P3 each bearing 7 setae …….. T. (Tortanus) Giesbrecht, 1898.
3’ – In both sexes, dorsal terminal triangular process absent on both caudal rami ; prosomal corners of female produced posteriorly into winglike process ; caudal rami of male shorter than urosomites compbined ; 2 nd endopod segments of legs P2 and P3 each bearing 8 setae ……T. (Eutortanus) Smirnov, 1935.
4 – In both sexes, pedigers 4 and 5 separate ; female P5 with with 1-segmented exopodbearing either 4 spines or 3 spines plus 1 process ; in right P5 of male, exopod arising proximally from basis …….. T. (acutanus) Ohtsuka, 1992.
4’ – In both sexes, pedigers 4 and 5 fused ; female exopod of P5 either reduced or 1-segmented, tapering distally with spines/processes ; in right P5 of male, exopod arising distally from basis …….. T. (Atortus) Ohtsuka, 1992.