Plate 1 issued from : E.L. Markhaseva in Proc. Zool. Inst. RAN, St. Petersburg, 1996, 268. [p.190, Fig.148].
Female (specimen from NW Pacif.: kuril Trench). Ce: forehead (lateral); R: rostrum (anterior); P.md: mandibular palp.
Nota: A1 as long as cephalothorax, or longer by 1-2 segments.

Male (from Brodsky, 1950).

Plate 2 Issued from : K.A. Brodskii in Calanoida of the Far Eastern Seas and Polar Basin of the USSR. Opred. Fauna SSSR, 1950, 35 (Israel Program for Scientific Translations, Jerusalem, 1967) [p.161, Fig.73]. As Gaidius brevirostris.
Female (from NW Pacif.): R, rostrum; corner of the last thoracic segment and urosome (lateral right side); Mp2, Mxp; S4B1, distal inner margin of basipodal segment 1 of P4.
Nota: Spines on posterior corners of last thoracic segment short, situated in the middle of posterior border (lateral view).

Male: S5, P5.

Plate 3
Gaetanus brevirostris female:
1 - Cephalon without frontal spine.
2 - Posterior corners of last thoracic segment with small spines.
3 - Exopodal segment 1 of A2 without setae; segment 2 with 2 setae. 2nd internal lobe of Mx1 with 4 setae. Exopod of P1 3-segmented with 2 external spines.
4 - Mxp protopodite without lateral plate.
5 - Md palp base with 2 setae.
6 - Exopod of P1 clearly 3-segmented.

Plate 4 Gaetanus brevirostris male:
1 - Cephalon without frontal spine.
2 - Cephalon without crest in anterior part.
3 - Exopodal segment 3 of left P5 stylet-like. Body size < 5 mm.
4 - Posterior corners of last thoracic segment with spines.
5 - Spines significantly shorter than the border of genital segment.
6 - Exopodal segment 3 of P5 with stylet-like narrow.
7 - Body size ± 4 mm.