Valettiopsidae

Broyer, De, 2008, Alicellidae and Valettiopsidae, two new callynophorate families (Crustacea: Amphipoda), Zootaxa 1843, pp. 57-66 : 64-65

Valettiopsidae new family

Type genus. Valettiopsis Holmes, 1908 .

Description. Head exposed; as long as deep or deeper than long; anteroventral margin concave, weakly recessed, moderately excavate; anteroventral corner subquadrate; rostrum vestigial or absent; eyes absent. Body laterally compressed.

Antenna 1 shorter than or subequal in length to antenna 2; peduncle 3-articulate, with sparse slender setae; peduncular article 1 longer than article 2; article 2 longer than article 3; peduncular articles not geniculate; accessory flagellum short; callynophore present; calceoli present or absent. Antenna 2 short or medium length; peduncle with many slender or sparse setae; without hook-like process; flagellum longer than peduncle, 5 or more articulate.

Mouthparts well developed, forming a subquadrate bundle. Mandible incisors symmetrical, dentate, curved; lacinia mobilis present on both mandibles (blade-like, broader than long, with serrate margin); molar strongly triturative; palp present. Maxilla 1 inner plate setose along medial margin; outer plate with 6/5 setal-tooth formula; palps symmetrical, 2-articulate. Maxilla 2 inner and outer plates subequal in length; inner plate with oblique setal row. Maxilliped inner plates well developed, separate; outer plate longer than palp article 1, not longer than palp article 2; palp 4-articulate.

Pereon. Pereonites 1–7 separate, complete; pleurae absent. Coxae 1–7 well developed, none fused with pereonites, overlapping, none ventrally acute. Coxae 1–3 well developed, none hidden or some coxae vestigial and hidden by other coxae. Coxae 2–4, none extensively broadened.

Gnathopod 1 similar in males and females; smaller (or weaker) than or similar in size to gnathopod 2; similar in form to gnathopod 2; subchelate; coxa smaller than or subequal to coxa 2, not produced anteroventrally; ischium elongate, 1.5- 2 x as long as broad; merus and carpus not rotated; carpus shorter than or subequal to propodus; dactylus large. Gnathopod 2 similar in males and females (not sexually dimorphic); subchelate; coxa subequal to but not hidden by coxa 3; ischium long; carpus/propodus not rectolinear; carpus long, not produced along posterior margin of propodus, projecting between merus and carpus; propodus without complex setae along posterodistal margin; propodus without complex setae along posterodistal margin; dactylus well developed.

Pereopods, none prehensile, 3–7 without hooded dactyli. Pereopod 3 coxa longer than broad; carpus shorter than or subequal to propodus, not produced; dactylus well developed. Pereopod 4 coxa subequal to or larger than coxa 3, not ventrally acute, with well developed or with small posteroventral lobe; carpus shorter than or subequal to propodus, not produced; dactylus well developed. Pereopods 5–7 with few robust or slen- der setae. Pereopod 5 shorter than or subequal in length to pereopod 6; coxa smaller than coxa 4, equilobate or with large or small anteroventral lobe; basis expanded, subrectangular, subquadrate or subovate, with or without posteroventral lobe; carpus linear; dactylus with setae absent. Pereopod 6 subequal in length to or longer than pereopod 7; basis expanded or slightly expanded; dactylus without setae. Pereopod 7 longer than pereopod 5, similar in structure to pereopod 6; basis expanded or slightly expanded, without dense slender setae; dactylus short (between 1/8 and1/4 length of propodus) or medium length (1/4 to 1/2 length of propodus).

Pleon. Pleonites 1–3 without transverse dorsal serrations, 1–2 each with or without dorsal spine, without lateral teeth or ridging, without dorsal carina. Epimeron 1 well developed. Epimeron 2 setose along ventral margin.

Urosome not dorsoventrally flattened; urosomites 1–3 free; urosomite 1 carinate or not. Urosomite 3 not fused with telson. Uropods 1–2 apices of rami without robust setae or setae embedded. Uropod 1 peduncle without long plumose setae; biramous. Uropod 2 well developed; without dorsal flange; inner ramus subequal in length to or longer than outer ramus. Uropod 3 not sexually dimorphic; without medial process; biramous; outer ramus longer than peduncle; inner ramus subequal to outer ramus. Telson longer than broad; deeply cleft; dorsal or lateral robust setae present or absent; apical slender setae absent; apical robust setae present.

Included genera. The Valettiopsidae includes 2 genera: Valettietta Lincoln & Thurston, 1983 ; Valettiopsis Holmes, 1908 .

Remarks. Valettiopsids are deep-sea scavengers, occurring from the continental shelf down to 4300 m depth. Valettiopsids have been compared to valettid amphipods ( Thurston 1989) which are close associates of deep-sea holothurians. Both families are callynophorate amphipods, both have curved dentate incisors, triturating molars, marginal setae along the inner plate of maxilla 1, elongate ischium on gnathopod 2, equilobate coxa on pereopod 5, no robust apical setae on uropods 1 and 2 and deeply cleft telsons. However valettids do not have an oblique setal row on the inner plate of maxilla 2, the outer maxillipedal plate does not have apical robust or slender setae and the telson is shorter and bears no setae.

Valettiopsids also show affinities to the Miramarassidae . Both have uropods 1 and 2 without apical robust setae, deeply cleft telsons, elongate ischia on the second gnathopods with rectolinear carpi and propodi, a lacinia mobilis on both mandibles, inner plates of maxillae 1 with setae along the medial margins and rami of third uropods longer than the peduncles. But among other differences the miramarassids apparently have no callynophore nor posteroventral lobe on the pereopod 4 coxa and the structure of the antenna 1 peduncular articles are different.

Valettiopsids also appear to be related to eusirids (sensu stricto). They differ in the well developed accessory flagellum (minute or scale-like in eusirids), in the inner plate of maxilla 1 which has setae along the entire medial margin (apical in eusirids) and in the long ischium on gnathopod 2 (short in eusirids).

Distribution. Known from about 50° north to 40° south in the Atlantic and Pacific Oceans, 183–6000 m depth. Also known from an anchialine cave in the Galapagos Islands, 17–29 m depth ( Stock & Iliffe 1990).