Giesbrecht, 1892
Females
Pr elongate to elongate-oval, or cyclopiform. Ce and Pd1 always separate. Ur generally slender, of 5 somites; genital apertures paired, located dorsally or laterally on anterior part of Gns and closed off by small operculae derived from vestigial P6; seminal receptacles paired; CR with 6-7 setae, seta I minute or absent, dorsal seta may or may not be inserted into dorsal expansion on ramus (Genus Conaea and Genus Epicalymma). Eggs carried in paired sacs. R fused to Ce; nauplius eye present; labrum well-developed, medially incised. A1 short 6-segmented (segments 3 and 4 fused); segment 4 of the compound segment 3 with sexually dimorphic seta. A2 uniramous, 3-segmented, subprehensile; with 2-segmented Enp, Enp1 without seta, Enp 2+3 with 3-4 lateral and 6-7 distal elements (Enp2 with maximum of 4 elements); Exp lacking; Co and Ba fused with long seta. Labrum bilobate, medially incised, with distinct teeth or scales medially. Md complex with 4-5 discrete distal elements; non lash-like; without palp. Mx1 small, bilobed; Li1 with 3 setae; outer lobe representing reduced palp, armed with 4 setae. Mx2 Ba drawn out into pinnate claw; with 1 outer and 2 inner elements. Mxp 4-segmented, Co without seta, Ba with 2 setae/spines; Enp1 small, Enp2 in the form of claw. P1-4 biramous with both rami 3-segmented; inner coxal seta absent; outer basal seta present.
Spine and seta formula:Spine and seta Oncaeidae.
P5 with protopod incorporated in somite and represented by dorsal seta on surface of somite (may be secondarily lost), Exp 1-segmented bearing 2 setae or 1 seta and spinule or sometimes entirely incorporate into somite; Enp absent. P6 represented by opercular plates bearing 1-2 setae or spines closing off genital openings.
Males
Ur of 6 somites, genital apertures paired, located posteroventrally on large Gns, apertures closed off by well-developed symmetrical flaps derived from vestigial P6. Gns voluminous, longer than postgenital somites combined. A1, Mxp P5 and P6 sexually dimorphic. A1 never geniculate, last 3 segments fused forming compound terminal segment, setation as in female except for absence of distal seta on 3rd segment; 3-6 segmented. A2 and mouthparts rarely reduced. Mxp Ba usually more robust and muscular in male than female, Enp represented by claw only. P6 represented by paired flaps at posterior of Gns with 0-1 elements.
This family now contains seven genera, not all of which have been taken in the South Atlantic:
Genus Archioncaea Boettger-Schnack and Huys, 1997
Genus Conaea Giesbrecht, 1891
Genus Epicalymma Heron, 1977
Genus Monthula Boettger-Schnack, 2001
Genus Oncaea Philippi, 1843
Genus Spinoncaea Boettger-Schnack, 2003
Genus Triconia Boettger-Schnack, 1999
Further genera are expected to be erected in the near future (see Huys and Boettger-Schnack 1996/97). Members of this family in the South Atlantic are badly in need of revision, especially Oncaea s.l.; many previous records cannot be confirmed against current knowledge of species because inadequate illustrations are provided. The present keys for Oncaeidae are tentative guides only. If a species cannot be identified from these keys, then a wider suite of species will have to be examined (see e.g. Heron and Bradford-Grieve 1995; Boettger-Schnack, 2003). The key includes species not yet taken in the South Atlantic (Heron and Damkaer, 1978). Pachos tuberosum (Giesbrecht, 1891) has also been included although it is not now considered to be an Oncaeidae (Heron and Damkaer 1978; Huys and Boettger-Schnack, 1996/97).
The key to genera and species of Oncaeidae starts at Page 1273: Copepoda: Family Oncaeidae of the key.