Aëtidiina Giesbrecht,1892 (p.52); Aetidiinae : Esterly, 1905 (p.143)

Sars, 1901 a (1903) (p.23); With, 1915 (p.72); Gurney, 1931 a (p.84); Rose, 1933 a (p.88); Brodsky, 1950 (1967) (p.82, 141); Vervoort, 1952 (n°41, p.2, Genera Key); Mazza, 1967 (p.106); 1968 (p.531); Bradford, 1969 b (p.473, 502: Table 3): Björnberg, 1972 (p.25); Andronov, 1974 a (p.1005); Campaner, 1978 (p.865); Bradford & Jillett, 1980 (p.11); Vaupel-Klein, 1982 a (p.1); Bowman & Abele, 1982 (p.9); Razouls, 1982 (p.153); 1993 (p.309); Brodsky & al., 1983 (p.144, 145, 147); Zheng Zhong & al., 1984 (1989) (p.235, genera Key); Mauchline, 1988 (p.426, 731, 740: cuticular pores); Huys & Boxshall, 1991 (p.460); Markhaseva, 1993 (p.51, phylogeny); Vyshkvartzeva, 1994 (p.118 & suiv.); Markhaseva, 1996 (p.3, Genera Key, Rem.: p.8); Madhupratap & al., 1996 (p.863, Table 5: %/copepods); Chihara & Murano, 1997 (p.681, Genera Key); Bradford-Grieve & al., 1999 (p.879, 903, 904, 917: Genera & spp. Key); Ohtsuka & Huys, 2001 (p.445, 461); Markhaseva & Schnack-Schiel, 2003 (p.116 & suiv., Rem.); Boxshall & Halsey, 2004 (p.12, 15, 16; 49; p. 54: Def.; p.57: Genera Key); Vives & Shmeleva, 2007 (p.533, part. Genera Key); Markhaseva & Schulz, 2008 (p.48, Fig.12: geographical distribution of benthopelagic genera); Blanco-Bercial & al., 2011 (p.103, Table 1, Fig.2, 3, 4, molecular biology, phylogeny); Laakmann & al., 2012 (p.535, Rem.: p.543, phylogeny); Markhaseva & Renz, 2015 (p.1041, Rem.: differences between Clausocalanidae and Aetideidae); Laakmann & al., 2019 (p.330, fig.1, 2, 3, Table A, phylogenetic relationships); Hirai & al., 2020 (p.1, Fig.4: metabarcoding, Fig.8: OTUs distribution patterns, Fig.9: phylogenetic analysis)

Type-genus: Aetideus Brady, 1883. Total: 30 G.: Aetideopsis, Aetideus, Azygokeras, Batheuchaeta, Bradyetes, Bradyidius, Chiridiella, Chiridius, Chirundina, Chirundinella, Comantenna, Crassantenna, Euchirella, Gaetanus, Gaidiopsis, ['Gaidius'= Gaetanus], Jaschnovia, Lutamator, Mesocomantenna, Paivella, Parabradyidius, Paracomantenna, Prolutamator, Pseudeuchaeta, Pseudochirella, Pseudotharybis, Pterochirella, Sursamucro, Undeuchaeta, Valdiviella.
Senecella represents the only brackish- and freshwater genus.
For Markhaseva (1996, p.8) this family comprises only 26 genera (with the new genus Parabradyidius); Gaidius is synonym with Gaetanus; Wilsonidius is considered as a synonym of Chirundina; Gaidiopsis is insufficiently described and the type species lost; Pseudotharybis is intermediate between this family and the Tharybidae; Valdiviella could constitute the type of a new Family.

Diagnosis from Boxshall & Halsey (2004, p.54) :
- Cephalosome and pedigerous somite 1 fused, or rarely with partial suture dorsally, pedigerous somites 4 and 5 sometimes separate.
- Rostrum variable, may be simple, bifid or divided into paired rostral filaments, rarely absent.
- Anterior part of cephalosome may form crest.
- Frontal cephalic spine present in some species of Gaetanus.
- Nauplius eye present.
- Last prosomal somite wometimes rounded, usually with pointed and posteriorly produced epimeral lobes.
- Urosome 4-segmented in female ; with 3 free abdominal somites.
Female genital double-somite symmetrical or asymmetrical, with common genital aperture located medially on ventral surface ; copulatory pore (s) contained within median genital aperture.
- Urosome 5-segmented in male ; single genital aperture located ventrolaterally at posterior rim of genital somite (1st urosomal segment) on left side.
- A1 23 to 25-segmented in female ; often longer than prosome ; segment 2 triple (II-IV), segments 8 (X) and 9 (XI) typically fused, segments 24 (XXVI) and 25 (XXVII-XXVIII) fused or separate. Aesthetascs typically present on segments III, VII, XI, XIV, XVI, XXI, XXVIII in female. A1 male typically non geniculate ; additional segmental fusions may include X-XI and XII , XV and XVI or XXIII and XXIV. Aesthetascs present on all segments dxcept I, XXII and XXV (based on Euchirella rostrata). Right A1 of male Azygokeras with 6 distal segments enlarged, possibly geniculate but mechanism may not be homologous with the neocopepoden geniculation.
- A2 biramous with separate coxa and basis ; coxa with 1 seta ; basis with 1 or 2 setae ; endopod 2-segmented, distal segment bilobed wuth maximum setation formula 2, 9+7, often reduced ; exopod usually larger than endopod, 7-segmented with compound segments I-II, III-IV and IX-X ; basic setation formula 2, 2, 1, 1, 1, 1,3, but setation sometimes reduced and additional segmental fusions sometimes present.
- Md biramous, coxa with well developed gnathobase and distal palp consisting of basis, 2-segmented ebndopod and 5-segmented exopod ; basis with 0 to 4 setae, usually 2 or 3 ; endopodal segments 1 and 2 wiyj up to 3 and 9 setae ; exopodal setation formula 1, 1, 1, 1, 2, setation often reduced.
- Mx1 with well developed praecoxal arthrite bearing 14 elements (9 distal spines, 4 posterior surface setae and 1 proximal seta) ; coxa with endite bearing 1 to 5, usually 4, setae and with 9 setae on epipodite ; basis without oiter seta, with small proximal endite bearing up to 5, usually 3 or 4 setae and distal group of 3 to 5 setae representing distal enditr ; endopod sometimes fused to basis, unsegmentrd to 3-segmented ; setation formula 4, 4, 7 ; exopod 1-segmented, usually armed with 9 to 11 setae ; maxillulary setation often very reduced as in Chiridiella/
- Mx2 7-segmented ; praecoxa and coxa separate, setation formula of endites 3, 3, 3, 3 ; basis with 3 setae including large claw-like element fused to basis ; free endopod 4-segmented, usually with 6 major setae but full setation formula 2, 3, 3, 3 ; maxilla highly modified in some Chiridiella species, carrying 2 or 3 strong, curved apical claws.
- Mxp 7-segmented, with distal part notated at synncoxa-basis joint ; syncoxa with endite setation formula 1, 2, 3, 4 ; most proximal seta sometimes absent ; 1 distal endite element sometimes modified, aesthetasc-like ; basis with 3 setae, plus 2 setae on incorporated 1st endopodal segment ; free endopod 5-segmented, segmental setation formula 4, 3, 3, 3+1, 4 ; setation often reduced ; syncoxa bearing large blade-like lateral pprocess in many Gaetanus species ; basis with strongly sclerotized outer margin in Chirundina.
- Male mouthparts often reduced compared to female.
- Swimming legs P1 to P4 biramous, typically with 3-segmented rami, except P1 with 1-segmented endoipod and P2 with 1 or 2-segmented endopod. P1 exopod 1-segmented in Chiridiella or 2-segmented in some species of Gaetanus and Euchirella ; additional segmental fusions sometimes present, as between proximal exopodal segmenys of Valdiviella species.
- Coxa of P4 ornamented with cluster of spinules near base of inner seta ; with 2 transverse rows of 4 to 6 spinules in Paivella, but usually lacking surface ornamentation except for scattered spinules.

Key to genera after Boxshall & Halsey (2004, p.57) ( modified from Markhaseva, 1996) :
Females:
1 – 5th pedigerous somite and genital double-somite symmetrical ……. 2.
1’ – Either 5th pedigerous somite or genital double-somite, or both, more or less asymmetrical …… 27.
2 – Rostrum present, not reduced ……. 3.
2’ – Rostrum absent or present as a reduced semi-circular plate …….. 15.
3 – Rostrum bifurcate ……… 4.
3’ – Rostrum conical, tapering to single point …… 9.
4 – Swimming legs typically with some degree of fusion between proximal segments of each ramus ; maxillulary endopod with at most 3 setae ……… Valdiviella.
4’ – Swimming legs without fusion of proximal segments ; maxillulary endopod with more than 3 setae ……… 5.
5 – P1 lacking outer spine on 1st exopodal segment ; Mx1 with 11 setae on exopod, and 3 setae on coxal endite ……. 6.
5’ – P1 with outer spine on 1st exopodal segment ; Mx1 with 8 to 11 setae on exopod, 4 or 5 setae on coxal endite …… 7.
6 – Coxa of P4 ornamented with 2 parallel rows of 4 to 6 spinules on posterior surface near base of inner seta ……. Paivella.
6’ – Coxa of P4 lacking such ornamentation on posterior surface …….. Aetideus.
7 – P5 3-segmented, distal segment with 3 spinous projections …… 31.
7’ – P5 vestigial or absent ……. 8.
8 – Outer margin spine on 2nd exopodal segment of P1 thicker than that on 1st segment ; P2 endopod always 2-segmented …….Bradyidius.
8’ – Outer margin spine on 2nd exopodal segment of P1 not markedly thicker than that on 1st segment ; P2 endopod either 1 or indistinctly 2-segmented ……. Aetideopsis.
9 – Coxa of P4 ornamented with spinules on posterior surface near base of inner seta ……… 11.
9’ – Coxa of P4 lacking such ornamentation of spinules near base of inner seta …….. 10.
10 – Mxp with conspicuous sclerotized thickening extending along outer margin of basis ; Mx1 with 11 setae on exopod, 15 on endopod and 5 on coxal endite ……. Chirundina.
10’ – Mxp without conspicuous sclerotized thickening on basis ; Mx1 with 10 setae on exopod, 11 on endopod and 4 on coxal endite …… Chirundinella.
11 – A2 endopod at most half as long as exopod ; Md basis unarmed ; Mx1 endopod with at most 5 setae …… Euchirella (part).
11’ – A2 endopod more than half as long as exopod ; Md basis armed with 1 or more setae ; Mx1 endopod with at least 14 setae ……. 12.
12 – Frontal margin of cephalosome with long spinous process ……… Gaetanus (part).
12’ – Frontal spinous process absent …….. 13.
13 – Mxp with blade-like process on lateral margin of syncoxa …….Gaetanus (part).
13’ – Mxp lacking outer blade-like process on syncoxa ……. 14.
14 – 4th and 5th pedigerous somites fused ; P1 exopod with 2 outer spines ; Md basis with ½ setae …….. Gaetanus (part).
14’ – 4th and 5th pedigerous somites usually sepatate ; P1 exopod with 3 outer spines ; Md basis with 3 setae ……. Pseudochirella (part).
15 – Distal syncoxal endite of Mxp with 1 modified, blunt-ending sensory element …… 23.
15’ – Distal syncoxal endite of Mxp lacking any modified, blunt-ending element …… 16.
16 – P1 exopod 1-segmented ; Mx2 often highly specialised, armed with strong, curved apical claws …….Chiridiella.
16’ – P1 exopod 3-segmented ; Mx2 lacking specialised apical claws …… 17.
17 – 1st exopodal segment of P1 lacking outer spine …… Jaschnovia.
17’ - 1st exopodal segment of P1 armed with outer spine …….. 18.
18 – 3rd exopodal segment of P2 to P4 with 3 outer spines …… 19.
18’ – 3rd exopodal segment of P2 to P4 with only 2 outer spines …….. Senecella calanoides.
19 – Posterolateral angles of prosome drawn out into conspicuous points or spinous processes ……. 20.
19’ – Posterolateral angles of prosome without conspicuous points or spinous processes ……. 22.
20 – Posterolateral prosomal processes directed straight backwards ; 4th and 5th pedigerous somites fused ; rostrum absent ……… Chiridius.
20’ – Posterolateral prosomal processes curved backwards ; 4th and 5th pedigerous somites separate ; rostrum reduced, in form of semi-circular blade …… 21.
21 – 2nd segment of Md endopod with 4 setae, basis unarmed ; A2 endopod better developed than exopod ……. Crassantenna.
21’ - 2nd segment of Md endopod with 9 setae, basis with 2 setae ; A2 endopod smaller than exopod ……. Sursamucro.
22 – Rostrum absent ; 2nd endopodal segment of Md with 10 setae, 1st endopodal segment with 2 setae, basis with 3 setae …….. Azygokeras.
22’ – Rostrum present in form of reduced semi-circular blade ; 2nd endopodal segment of Md with 4 or 5 setae, 1st endopodal segment and basis unarmed ……. Lutamator.
23 – A2 exopod shorter than endopod ……. 24.
23’ – A2 exopod as long as, or longer than, endopod ……. 26.
24 – Distal segment of A2 exopod shorter than preceding 2 segments combined ; 1 or more of terminal antennary exopodal setae much shorter than others, or only 1 seta present ….. 25.
24’ – Distal segment of A2 exopod longer than preceding 2 segments combined ; all terlinal antennary exopodal setae similar in length ……. Paracomantenna.
25 – Distal segment of A2 exopod armed with 3 setae ……. Comantenna.
25’ – Distal segment of A2 exopod armed with single apical seta ……..Mesocomantenna.
26 – 1st exopodal segment of P1 with outer spine present, not reduced ; setae on free endopodal segments of Mxp ornamented with modified crescent-like spinules ; setae on syncoxal and basal endites, and on endopod of Mx2 sabre-like, not transformed into claw …… Pseudeuchaeta.
26’ – 1st exiopodal segment of P1 without outer spine, or outer spine reduced ; setae on free endopodal segments of Mxp without crescent-like spinules ; setae on syncoxal and basal endites, and on endopod of Mx2 not sabre-like , at least 1 seta on basal endite trnsformed into claw …… Bradyetes.
27 – Rostrum absent or vestigial ……. 28.
27’ – Rostrum oresent, well developed …… 29.
28 – Md basis with 2 setae ; distal syncoxal endite of Mxp with 3 setae only, lacking modified element ……. Senecella siberica.
28’ – Md basis with 3 setae ; distal syncoxal endite of Mxp with 3 setae plus 1 modified, blunt-ending sensory element ……. Batheuchaeta.
29 – Coxa of P4 ornamented with spinules on posterior surface near base of inner seta ; exopod of P1 armed with 3 outer margin spines …… 30 .
29’ – Coxa of P4 ornamented without spinules on posterior surface near base of inner seta ; exopod of P1 armed with 2 outer margin spines …… Undeuchaeta.
30 – Exopod of P1 2-segmented ; Md basis lacking setae, 1st endopodal segment unarmed or 1 small seta …….. Euchirella (part).
30’ – Exopod of P1 3-segmented ; Md basis with 3 setae, 1st endopodal segment with 2 or 3 setae …….. Pseudochirella (part).
31 – Md basis with 2 setae ; rami of A2 subequal in length, or exopod slightly shorter than endopod ……. Parabradyidius.
31’ – Md basis with 3 setae ; exopod of A2 distinctly longer than endopod ……. Pseudotharybis.

Males :
1 – Rostrum present …….. 9.
1’ - Rostrum absent …… 2.
2 – Right A1 apparently geniculate, with distal 6 segments enlarged …… Azygokeras.
2’ – Both A1 non-geniculate, without enlarged segments distally ……. 3.
3 – P56 present on left side only, uniramous …… Aetideus.
3’ – P5 present on both sides ; legs P5 uniramous or biramous ….. 4.
4 – Legs P5 uniramous, left leg 5-segmented, right leg 4-segmented ……Chiridius.
4’ – Legs P5 biramous, left exopod 3-segmented, right exopod 2 or 3-segmented ……. 5.
5 – Exopod of right P5 3-segmented ……. 8.
5’ – Exopod of right P5 2-segmented …… 6.
6 – 3rd exopodal segment of left P5 stylet-like distally ; left endopod –segmented, not more than 1/3 as long as 1st exopodal segment of left leg …… Jaschnovia.
6’ – 3rd exopodal segment of left P5 not stylet-like distally ; left endopod typically 2-segmented, or if 1-segmented then longer than 1st exopodal segment ……. 7.
7 – 2nd exopodal segment of right P5 filament-like distally, ornamented with long hair-like setules ……… Comantenna.
7’ – 2nd exopodal segment of right P5 not filament-like distally, lacking hair-like ornamentation ….. Bradyetes.
8 – Dorsal cephalic shield with marked transverse cleft about at level of mandibular somite and with paired posterodorsal wing-like projections ……. Pterochirella.
8’ – Dorsal cephalic shield lacking conspicuous transverse cleft and dorsal projections …… Chiridiella.
9 – Rostrum bifurcate ….. 10.
9’ – Rostrum conical, tapering to single point …… 17.
10 – Posterolateral angles of prosome rounded ….. 11.
10’ – Posterolateral angles of prosome tapering to spinous processes or with tiny spinous tooth ….. 12.
11 – Legs P5 uniramous ; left leg elongate, right leg short …… Paivella.
11’ – Legs P5 biramous with 3-segmented exopods and 1-segmented endopods ……. Valdiviella.
12 – Legs P5 uniramous or biramous ; posterolateral angles of prosome forming short spinous processes or tooth not reaching to posterior margin of genital somite ….. 13.
12’ - Legs P5 biramous ; posterolateral angles of prosome with well developed spinous processes extending posteriorly to posterior margin of genital somite …… 16.
13 – Legs P5 with 3-segmented exopods and indistinctly 2-segmented endopods ……. Parabradyidius.
13’ – Legs P5 with at least one exopod 2-segmented and one endopod 1-segmented ….. 14.
14 – Legs P5 with 3-segmented left exopod ……. 15.
14’ – Legs P5 with 2-segmented left exopod and 3-segmented right exopod ……. Bradyidius (part).
15 – Rostrum bifurcate with divergent branches ……… Pseudotharybis.
15’ – Rostrum bifurcate with closely adpressed, parallel branches ……. Aetideopsis (part).
16 – Legs P5 with 2-segmented right exopod and 3-segmented left exopod …… Aetideopsis (part).
16’ – legs P5 with 3-segmented right exopod and 2-segmented left exopod ……. Bradyidius (part).
17 – Basis of right P5 swollen, almost circular in outline ; left exopod complex with swollen irregular segments, left endopod irregular, tapering proximally …… Senecella ;
17’ – legs P5 not of this form, basis and ramal segments typically cylindrical …….. 18.
18 – Rostrum rudimentary ; exopod of right P5 3-segmented ………. Pseudeuchaeta.
18’ – Rostrum not rudimentary ; exopod of right P5 2-segmented …….. 19.
19 – Frontal margin of cephalosome with spinous process ……. Gaetanus (part).
19’ – Frontal margin of cephalosome without spinous process ……. 20.
20 – basis of left P5 with 2 processes on inner margin …… Batheuchaeta.
20’ – Basis of left P5 without processes on inner margin …… 21.
21 – Right P5 with elongate endopod and 2nd exopodal segment forming chela-like mechanism …… Euchirella (part).
21’ – Right P5 not forming chela-like mechanism ……. 22 ;
22 – Dorsal cephalic shield with crest …….. 23.
22' - Dorsal cephalic shield without crest ……. 25.
23 – P1 exopod 2-segmented ……... Euchirella (part).
23' - P1 exopod 3-segmented …….. 24.
24 – 3rd exopodal segment of left P5 bilobed ; 1st exopodal segment of P1 with outer spine ….. Chirundinella.
24’ – 3rd exopodal segment of left P5 not stylet-like distally, more triangular in outline ; 1st exopodal segment of P1 with or without outer spine …….. Chirundina.
24’’ – 3rd exopodal segment of left P5 stylet-like distally ; 1st exopodal segment of P1 without outer margin spine ……. Undeuchaeta (part).
25 – Left P5 lacking teeth on 2nd exopodal segment ; without processes on other segments of both rami, or with general complex configuration ……… 26.
26 – P1 exopod 2-segmented ……… Euchirella (part).
26’ – P1 exopod 3-segmented ……. 27.
27 – 1st exopodal segment of P1 with outer spine ……… Pseudichirella.
27’ – 1st exopodal segment of P1 without outer spine …… Undeuchaeta (part).

For Schulz & Markhaseva (2000, p.87) the genus Parabradyidius differs from Aetideopsis, Bradyidius, Pseudotharybis in relative length of A2 endo- and exopod: while in these three genera the exopod is distinctly longer than the endopod (ca. 1.2 - 1.5 times), in Parabradyidius these rami are subequal or the exopod may be even slightly shoryter. In addition, Parabradyidius lacks the medial seta of the A2 7th exopodal segment present in these three taxa.
The male of the new genus is the only aetideid male known so far to have both exopods of P5 equipped with 3-segmented rami as well as, indistinctly , 2-segmented endopods. Such segmentation can be considered the most primitive among Aetideidae. Only Azygoceras, Chiridiella, Pseudeuchaeta share 3-segmented exopods on both rami, while P5 endopods are 1-segmented in these three genera. 2-segmented left endopod is typical only of the aetideids Bradyetes matthei, Bradyidius arnoldi, Comantenna brevicornis. All remaining aetideids share a 1-segmented endopod (if present at all) in the male. However, in Parabradyidius angelikae exopodal segment 3 of the left ramus is much more specialized than that in all other Aetideidae in that it has a deep excavation furnished with short hairs at the medial inner part of the segment, opposed to a segment of cylindrical shape lacking any excavation in remaining taxa. This combination of plesiomorphic as well as apomorphic characters appears to be a general feature of benthopelagic copepod taxa.