1	Leg 1 with 3 inner setae on distal exopod segment lost or highly reduced	C. productus group
–	Leg 1 with 3 inner setae on distal exopod segment well developed	2
2	Large denticles present along outer margin of second endopod segment of leg 2	C. bonito group
–	Large denticles absent along outer margin of second endopod segment of leg 2	3
3	Leg 4 is 4-segmented (3-segmented exopod)	4
–	Leg 4 is 3-segmented (2-segmented exopod)	5
4	Long-bodies; apron of leg 3 with raised bifid cuticular rib and rosette-like array of denticles	C. confusus group
–	Compact bodies; apron of leg 3 without such ornamentation	C. diaphanus group
5	Distal exopod segment of leg 4 with 1 outer and 3 terminal spines	C. pseudorhombi group
–	Distal exopod segment of leg 4 with 3 terminal spines	C. macarovi group