Cyclocaridae Lowry & Stoddart 2011, fam. nov.

Cyclocaridae fam. nov.

(Fig. 5)

Diagnostic description. Head exposed, slightly deeper than long, without cheek notch. Antennae calceoli present or absent in male. Antenna 2 peduncular article 3 without distal hook. Epistome and upper lip separate. Epistome with proximal portion not produced. Mouthpart bundle subquadrate. Mandible incisors well developed, incisors asymmetrical, left straight, minutely serrate, right convex, smooth; left lacinia mobilis rod-like; accessory setal row with more than 5 robust setae, without distal setal tuft; molar a setose tongue; palp inserted distally. Maxilla 1 inner plate with pappose setae along medial margin; outer plate with setal-teeth in 7/4 crown arrangement, setalteeth large; palp large, with apical robust setae. Maxilla 2 inner plate significantly shorter than outer plate, inner plate without oblique row of facial setae. Maxilliped outer plate present, medial setae small, blunt or bead-shaped, with apical slender setae; palp 4-articulate, article 4 well-developed.

Gnathopod 1 simple; coxa vestigial; ischium long; carpus long; propodus small; dactylus slightly curved. Gnathopod 2 coxa vestigial. Pereopods all simple; distal spurs absent. Pereopod 4 coxa with posteroventral lobe weak or absent. Pereopod 5 coxa anterior and posterior lobes subequal.

Uropod 3 biramous. Telson cleft.

Type genus. Cyclocaris Stebbing, 1888.

Included genera. Cyclocaridae includes only one genus: Cyclocaris Stebbing, 1888.

Remarks. As discussed above, cyclocarids appear to be most similar to cebocarid amphipods. Cyclocarids differ significantly from cebocarids in the head which is only slightly deeper than long, in the eyes which cover most of the head, in the mandible which has more strongly asymmetrical incisors and a setose molar and in the simple, non-prehensile pereopods. We have examined material of Cyclocaris tahitensis collected at the Austral Isles (reported by Lowry & Stoddart 1994) and found that the head shape, when fully exposed, is similar to that of C. guilelmi. There is also evidence of a very large eye which had faded with preservation (see fig. 5H female, AM P.42130).

In contrast to the possibly-egg-eating cebocarids, members of the Cyclocaridae are abundant deep-sea scavengers known from the northern and southern hemispheres in the Atlantic and Pacific Oceans. They are unusual among lysianassoid taxa in having eyes covering the whole head, a situation similar to some hyperiidean taxa. This might indicate that cyclocarids are predators as well as scavengers. Cyclocarids have been taken in the water column (490–2857 m), but they also live near the bottom: Lowry & Stoddart (1994) reported C. tahitensis Stebbing, 1888 from baited traps set on the bottom in 65 to 870 m depth.