Trianguloscalpellum hirsutum Hoek 1883

Trianguloscalpellum hirsutum (Hoek, 1883)

Figures 1 F, 9

Scalpellum hirsutum Hoek, 1883: 88, pl. 4 fig. 19. — Newman & Ross, 1971: 63, fig. 28. Trianguloscalpellum hirsutum. — Zevina, 1981: 309, fig. 233.

Material examined. NMNS 005087-00082, 1 specimen, Stn. CP300 (22º17.156’N, 119º59.963’E, 11 Aug. 2005, depth: 960–972 m), CL 20.03 mm, CW 12.76 mm, PL 8.54 mm; CEL-BB-26B, 1 specimen, Stn. CP375 (24º16.240’N, 122º11.720’E, 27 Aug. 2006, depth: 2216–2497 m), CL 21.38 mm, CW 19.42 mm, PL 13.78 mm; CEL-BB-63, 1 specimen, Stn. CP371 (24º28.521’N, 122º12.821’E, 26 Aug. 2006, depth: 582–613 m), CL 21.5 mm, CW 13.2 mm, PL 12.03 mm.

Diagnosis. Capitulum with 14 fully calcified plates; surface of capitulum and peduncle covered by dense setae; tergum with long, sharp apex, upper latus triangular

Description. Capitulum with 14 fully calcified plates, surfaces covered by long setae (Fig. 1 F); tergum large, elongated rhomboid, higher than wide, apex apical, produced, acute, umbo apical, occludent margin straight; scutum quadrangular, occludent and tergal margins convex, lateral and basal margin straight, apex produced at tip of occludent margin, umbo apical (Fig. 1 F); upper latus triangular, carinal margin straight; inframedian latus triangular, subequilateral, umbo apical; rostrolatus flattened, width twice height (Fig. 1 F); carinolatus horn-shaped, apex apical, produced, touching carina. Peduncle short, scales in longitudinal rows. Maxilla bilobed, setae in 3 main clusters (Fig. 9 A); maxillule not notched, cutting edge with ~ 19 cuspidate setae on cutting edge (Fig. 9 B); mandible with 3 equally spaced teeth, lower margin straight, smooth, inferior angle blunt with dense setae (Fig. 9 C); mandibular palp elongated, setae on superior margin and apically (Fig. 9 D); labrum concave, cutting edge smooth, with fine setae, teeth absent (Fig. 9 E, I). Cirrus I separated from cirri II-VI, rami unequal, outer ramus longer, slender, (13-segmented), inner ramus shorter, broad (7- segmented) (Fig. 9 F); cirrus II with rami subequal, outer ramus 23-segmented, inner ramus 25-segmented (Fig. 9 G); cirri III–VI similar length, longer than cirri I and II, cirrus IV with outer ramus 26-segmented, inner ramus 25-segmented (Fig. 9 H); caudal appendage 1-segmented, appendage length <height of basal segment of pedicle of cirrus VI.

Distribution. Borneo, Antarctica and Taiwan.

Remarks. This is a new record for Taiwanese waters. Trianguloscalpellum hirsutum is morphologically close to Arcoscalpellum foresti Rosell, 1989, in that both species have setae on the whole body, and in the shape of the tergum. Trianguloscalpellum hirsutum has a triangular upper latus, whilst that of A. foresti is quadrangular. The umbo of the carinolatus of A. foresti is located in the middle of the carinal margin, whilst that of T. hirsutum is located apically.