Giesbrecht, 1892
Females
Pd4 and 5 fused in majority of genera. R, if present, 2-pointed, or in form of blunt plate, or conical and 1-pointed. Posterior corners of Pr symmetrical or asymmetrical, rounded or pointed, sometimes extended into spines of various size and configuration or in lobes of various shapes. Gns symmetrical or asymmetrical, sometimes with 1-2 spines; ventral swelling more or less pronounced. A1 23-24-segmented, of various lengths. A2 Exp 7-segmented; Exp1 with 1-2 setae or without setae; sometimes Exp1 and Exp2 (Euchirella) fused completely or incompletely, or Exp2 and Exp3 (Comantenna, Mesocomantenna) partly fused; Exp2 with 1-3 setae, or setae absent (Chiridiella, Comantenna, Euchirella). Mdp Basis with 2-3 setae; sometimes with 1 seta, or without setae; Enp1 with 1-3 or without setae; Enp2 with 9 terminal and 1-2 posterior setae, sometimes this number differs; Exp 5-segmented, Exp1-4 with 1 long seta each; Exp5 with 2 terminal setae. Mx1 Li1 with 9 terminal setae, 1 shorter anterior seta and 4 setae on posterior surface (sometimes number of posterior setae is fewer); Li2 with 3-5 setae, rarely with 2 or 1 seta in Chiridiella this lobe may be reduced; Li3 with 3-4 setae; Enp with 14-16 setae, or fewer: 3-5 or 7 in Chiridiella, 10 or 11 in Paivella and 3 or 5 in Euchirella; Exp in most genera with 11, rarely with 8-10 setae, but in Chiridiella this number is 3-6 and Exp may be reduced. Mx2 usually with 5 well-developed Li (6 Li in Jaschnovia, Senecella and some species of Aetideopsis), Enp with 6 long setae, sometimes with additional small setae; Li1-5 with 2 long and 1 short plumose seta; one of two long setae on Li5 (rarely also on Li4) thickened and transformed into claw-like spine. Two genera have Mx2 strongly deviating from typical structure: in Pseudeuchaeta setae on Li4 and Li5 and on distal part of Enp are more sclerotized and sabre-like; and in Chiridiella Mx2 highly transformed. Mxp Coxa with 1 proximal seta (sometimes absent), with groups of 2, 3 and 3 setae from proximal to distal. P1 Enp outer lobe well developed, with small spinules terminally, rarely with hairs instead of spinules (Pseudeuchaeta); outer lobe absent in Chiridiella (except Coxa. kuniae). Posterior surfaces of Enp and Exp sometimes with fine small spinules, larger spinules on lateral borders of Coxa and Basis (Bradyidius, Jaschnovia). Majority of genera without spines or spinules on P4 Coxa, but sometimes with spines: 2 parallel transverse rows of 4-6 spines (Paivella); or bush-like spines near base of inner seta (Gaetanus, Pseudochirella, Euchirella), or only few small spinules (some species of Aetideus and Undeuchaeta).
Typical spine and seta formula: Spine and seta Aetideidae.
P5 absent (except for weak P5 in Comantenna recurvata and vestigial P5 found in some specimens of Sursamucro and Aetideopsis).
Males
Pd4 and 5 usually fused, sometimes incompletely (Aetideopsis, Azygokeras). R, if present, two-pointed, or conical (1-pointed). Crest may be present or absent. Posterior corners of Pr symmetrical, rarely somewhat asymmetrical (some Pseudochirella and Undeuchaeta species), of various shape. Ur of 5 free somites; Ur5 sharply reduced; genital opening on left. A1 usually 23-24-segmented, but sometimes 20-21-segmented (Aetideus); in all genera, except Azygokeras, not geniculated; with aestetasks in most species. Left and right A1 may have different number of segments. A2 as in female, but with fewer setae on Exp1, Exp2 and Enp; some setae of Mdp reduced in size. Mx1 and Mx2 very reduced. Mxp less well equipped with setae than in females. P1-P4 segmentation more pronounced than in females (i.e. when female has indistinct division, male has complete division). P1 Exp spines and setae as in female, but sometimes external spines reduced, occasionally absent. P4 Coxa without spines. Right and left P5 usually present, sometimes right P5 absent (Aetideus). P5 biramous or uniramous. If biramous, with Exp 3-segmented on left and 2-segmented on right (in Azygokeras, Chiridiella and Pseudeuchaeta right Exp 3-segmented). Both left and right Enp1-segmented (left Enp 2-segmented in Bradyetes matthei, Bradyidius arnoldi and Comantenna brevicornis).
The Aetideidae were recently reviewed by Markhaseva (1996) and all keys are adapted from this review. There are 26 genera in the family; 16 of these (marked * below) are known to occur in the South Atlantic and are given in the Key:
Genus Aetideus Brady, 1883*
Genus Aetideopsis Sars, 1903*
Genus Azygokeras Koeller and Littlepage, 1976
Genus Batheuchaeta Brodsky, 1950*
Genus Bradyidius Giesbrecht, 1897
Genus Chiridiella Sars, 1907*
Genus Chiridius Giesbrecht, 1892*
Genus Chirundina Giesbrecht, 1895*
Genus Chirundinella Tanaka, 1957*
Genus Comantenna Wilson, 1924*
Genus Crassantenna Cole et al., 1972
Genus Euchirella Giesbrecht, 1888*
Genus Gaetanus Giesbrecht, 1888*
Genus Jaschnovia Markhaseva, 1980
Genus Lutamator Bradford, 1969*
Genus Mesocomantenna Alvarez, 1986*
Genus Paivella Vervoort, 1965*
Genus Paracomantenna Campaner, 1978*
Genus Pseudeuchaeta Sars, 1905
Genus Pseudochirella Sars, 1920*
Genus Pterochirella Schulz, 1990
Genus Senecella Juday, 1923
Genus Sursamucro Bradford, 1969
Genus Undeuchaeta Giesbrecht, 1888*
Genus Gaidiopsis A. Scott, 1909 (however, poorly described).