Calanoidea: Families

J.M. Bradford-Grieve


Ridgewayiidae Wilson, 1958

Description. Female. Rostrum with 2 filaments, or without filaments; rostral margin extends into 2 points, or extends into 1 point, or extends into 1 blunt protrusion. Cephalosome and pedigerous somite 1 separate; pedigerous somites 4 and 5 separate. Posterior corners of prosome in lateral view bluntly rounded; dorsal view symmetrical. Urosome with 3 free somites, or with 4 free somites. Genital double-somite symmetrical in dorsal view, or asymmetrical in dorsal view; gonopores close together and totally covered by single genital operculum; without seminal receptacles. Caudal rami symmetrical.

Mouthparts. Antenna 1 with 23-26 free segments; ancestral segments X and XI separate. Antenna 2 exopod with 6-8 free segments; 9-11 setae; with 3 terminal setae, or with 4 terminal setae; basis and endopod separate. Mandible basis without setae, or with 4 setae; endopod terminal segment with 6 setae, or 9 setae, or 10 setae, or 11 setae. Maxilla 1 basal exite seta present; exopod extends short of endopod distal border. Maxilla 2 coxal epipodite seta absent. Maxilliped with normally-developed coxa, basis and endopod; coxal endite 2 with 2 setae, or with 3 setae, or with 4 setae.

Legs. Leg 1 basis outer seta absent; endopod with 3 segments; exopod with 3 segments; exopod segment 1 with outer distal spine; exopod segment 3 with 4 inner setae. Leg 2 endopod with 3 segments; exopod with 3 segments; exopod segment 3 with 2 outer spines. Leg 3 basis outer distal spine present; endopod segment 3 with 8 setae. Legs 3 and 4 endopod with 3 segments; exopod with 3 segments; exopod segment 3 with 3 outer spines; exopod segment 3 with 5 inner setae. Leg 4 endopod segment 3 with 7 setae. Legs 2-4 surfaces naked; terminal spine with outer border serrated. Leg 5 present; similar to legs 2-4; coxa inner border without seta; exopod segment 2 inner distal border with ordinary seta. Leg 5 exopod segment 3 inserted subterminally on inner border of segment 2; outer border with 3 spines; inner border with 3 setae, or 4 setae.

Mode of life. Benthopelagic, in coastal waters or in anchialine caves.

Distribution on sea floor. Less than 100 m.

Generic composition. This family now contains 4 genera: Brattstromia Fosshagen & Iliffe 1991; Exumella Fosshagen, 1970; Placocalanus Fosshagen, 1970; Ridgewayia Thompson & Scott, 1903.


(Variant) Male (sexually dimorphic characters).

Description. Male. Pedigerous somites 4 and 5 fused or partly fused, or separate.

Mouthparts. Mouthparts well-developed. Antenna 1 geniculate on right; geniculation between ancestral segments XX and XXI. Maxilliped endopod segments 5 and 6 with outer setae normal.

Legs. Right leg 5 biramous; endopod separate from basis and 1-segmented, or 3-segmented; exopod narrow relative to left leg 5, usually 2-segmented. Left leg 5 biramous; endopod 1-segmented, or 2-segmented, or 3-segmented; exopod similar to right leg or much wider, usually 3-segmented, terminal part may be short and of complicated structure, bearing lobes and spines.



Cite this publication as: 'Bradford-Grieve, J.M. (2002 onwards). Calanoida: families. Version 1: 2 October 2002. http://crustacea.net'.