Sars, 1905
Females
Total length 2.1-9.6 mm. Body usually slender, Pr oval, Ur relatively small proportion of total length, Ce and Pd1 separated, Pd4 and 5 fused, posterolateral corners and anterior Ce usually rounded but sometimes pointed. R filaments slender or absent, R sometimes represented by small knob. Ur usually short, of 3-4 somites; Gns with ventral swelling, CR symmetrical with 6 setae. A1 symmetrical, 24-25-segmented. A2 Coxa with 1 outer seta; Basis usually elongate with 1-2 outer edge setae; Exp and Enp separated from Basis; Enp 2-segmented, usually but not always much longer than Exp, Enp1 with 1-2 setae placed towards the distal end, Enp2 with 4-7 inner setae medially and 6-7 setae terminally; Exp 5-8-segmented, with varying numbers of setae: from 4 terminal setae, to every segment with at least 1 seta. Md gnathobases more usually symmetrically developed on each side with 2-7 (or more) short or long teeth set either obliquely or more or less at right angles to axis of gnathobase, in Pachyptilus and Heteroptilus gnathobases asymmetrically developed; Enp usually 2-segmented, sometimes 0- or 1-segmented, with varying number of setae; Exp usually 4-5-segmented with varying numbers of setae. Mx1 variable from full complement of lobes, with reduced setation distally in Haloptilus, Pontoptilus, Pachyptilus, and Heteroptilus, to extreme but variable reduction in at least outer and terminal lobes. Mx2 Li1-4 small and usually furnished with long setae, carrying characteristic shield-shaped appendages or, in case of Augaptilina, Li5 and Enp carries dense elongate bunches of setae resembling brush. Mxp Coxa with 3-10 setae; Basis slender or squat with 2 setae medially; Enp 6-segmented, sometimes elongate, Enp1 almost fully incorporated into Basis with 1-2 setae, Enp2-5 with 3-4, 3-4, 2-4, 1-4 setae respectively, Enp6 with 2-4 setae the outermost 1-3 of which are reduced. P1-4 with Exp 3-segmented, Enp usually 3-segmented except for P5 in Pontoptilus and few Euaugaptilus where it is 2-segmented and in Pachyptilus and Heteroptilus where it is 1-segmented; occasionally P1 Enp 2-segmented (some Euaugaptilus, Heteroptilus, Pachyptilus, and Augaptilina).
Spine and seta formula: Spine and seta Augaptilidae.
P5 natatory, symmetrical, very similar to other swimming legs but smaller than P2-4; inner edge seta on Exp2 often spine-like and articulated with its segment.
Males
Body similar to female, but Ur of 5 somites. Left A1 geniculate, ?21-22-segmented sometimes geniculate on right. Mouthparts and P1-4 similar to the female. P5 with 3-segmented Enp and Exp on left and right, slightly asymmetrical; right Exp2 often with inner expansion of variable shape but usually in form of thick spine.
The following genera are now in this family, of which Augaptilina, Heteroptilus and Pseudaugaptilus have not been recorded from the South Atlantic:
Genus Augaptilina Sars, 1920
Genus Augaptilus Giesbrecht, 1889
Genus Centraugaptilus Sars, 1920
Genus Euaugaptilus Sars, 1920
Genus Haloptilus Giesbrecht, 1898
Genus Heteroptilus Sars, 1920
Genus Pachyptilus Sars, 1920
Genus Pontoptilus Sars, 1905
Genus Pseudaugaptilus Sars, 1907
Matthews (1972) made an excellent review of the species of Euaugaptilus, Augaptilus, Haloptilus, and Pseudaugaptilus known to that date. Data on the distribution of setae on Mx1 in particular, used in the keys, are from his Table 5 (Matthews, 1972) and might not always agree with the figures reproduced here.