Arcoscalpellum radiatum Rao & Newman, 1972

Poltarukha, Oleg P. & Mel’Nik, Vyacheslav F., 2012, New records of deep-sea barnacles (Cirripedia: Thoracica: Scalpelliformes) from the Clarion-Clipperton region, Pacific Ocean, Zootaxa 3297, pp. 34-40 : 36-38

Arcoscalpellum radiatum Rao & Newman, 1972

Figure 2

Arcoscalpellum radiatum Rao & Newman, 1972: 80 , fig. 6. — Zevina, 1981b: 327, fig. 249. — Young, 2007: 68.

Material examined. Mg-1216, 1 specimen, stn 215 (13°55’.612N, 129°05’.519W), 28 Jul. 2003, depth 4680m.

Diagnosis. 14 fully calcified capitular plates; radial ribs prominent, emanating from umbones; cuticle with long setae. Umbo of carinolatus not recurved, not extending over lateral margin of carina. Carinal roof flat. Basal margin of inframedian latus much shorter than lateral margin.

Description. Capitulum white, elongate; cuticle with long, sparse setae. Capitular plates with distinct growth lines, prominent radial ribs emanating from umbones. Tergum triangular, umbo apical; occludent margin slightly convex, basal and carinal margins almost straight. Scutum large, quadrangular; apex slightly recurved, extending over tergum; occludent and carinal margins slightly convex, subparallel. Carina regularly arched, base broad, roof flat, lateral margins broad, well developed. Upper latus quadrangular; apex acute, straight; scutal margin slightly concave, other margins almost straight. Carinolatus higher than wide; plates contiguous under carina, interdigitating. Inframedian latus triangular, about 4 times higher than wide, umbo apical. Rostrolatus trapeziform; upper margin longer than basal. Rostrum well developed, broad. Peduncle short, approximately one third length of capitulum, covered by large scales. Labrum bullate, crest with sharp triangular teeth. Labial palp long, setose. Mandible with 3 acute teeth, lower angle strongly denticulate with 8 pointed teeth. Cutting edge of maxilla I with wide notch, upper part with 2 large and 2 small setae, lower part with 2 large and 3 medium setae. Maxilla II subtriangular, covered with few setae. Cirrus I with outer ramus slightly longer, 8-segmented, inner ramus 7-segmented; both rami covered by plumose setae. Cirrus II with outer ramus 10-segmented, inner ramus 12-segmented. Cirrus III with outer ramus 14-segmented, inner ramus 14-segmented. Cirrus IV with outer ramus 15-segmented, inner ramus 16-segmented. Cirrus V with outer ramus 16-segmented, inner ramus 16-segmented. Cirrus VI with outer ramus 16-segmented, inner ramus 17–segmented; medial segments of cirrus VI clothed with 3 groups of setae on ventral margin, two upper groups consisting of 1-2 long, thin setae and several short setae, lower group with short setae, upper dorsal angle with 1–2 long setae. Caudal appendage uniarticulate, shorter than basal segment of cirrus VI.

Distribution. Pacific Ocean: Mid-Pacific Mountains (18°30’N, 179°36’W); Clarion-Clipperton region; depth 1413–4680m.

Remarks. This is a new record for the Clarion-Clipperton region of the Pacific Ocean.

Figures

FIGURE 2. Arcoscalpellum radiatum Rao & Newman, 1972. A. Left side view, B. External view from rostral side, C. External view from carinal side, D. Labrum, E. Labial palp, F. Mandible, G. Maxilla I, H. Maxilla II, I. Caudal appendage.