Bairdoppilata scaura Maddocks, 2015, n. sp.

Bairdoppilata scaura n. sp.

(Figs. 6–11)

Etymology. Latin scaurus, with swollen ankles, club-footed; referring to the short antennal claws.

Material. Five specimens, including two males and three juveniles.

Types. Holotype male specimen 3360M, paratype male specimen 3864M, juvenile instar A- 1 specimen 3959J, and two undissected juveniles.

Type locality. Station FFS-TC-06 on French Frigate Shoals.

Dimensions. Holotype male specimen 3860M, entire carapace measured before dissection: Length 897 µm, height 500 µm. See also Table 1 and Figures 2 and 4.

Diagnostic description. Carapace smooth; oblong-subovate in lateral outline, with subangulate dorsal margin, greatest height located at rounded anterodorsal corner, at 0.49 of length; rounded posterodorsal corner located at 0.84 of length; anterodorsal brim located at 0.02 of length and 0.61 of height; posterodorsal brim located at 0.98 of length and 0.39 of height; highest point of ventral indentation located at 0.41 of length and 0.08 of height. Slope (measured from horizontal) of anterodorsal margin 26o, of mid-dorsal margin 21o, of posterodorsal margin 55o, of dorso-caudal margin 55o, of hinge 15o. No caudal process.

Antennal claws very short, about 0.38 of length of podomere 5; accessory claw slightly longer than main claw (1.10) and very nearly as wide (0.88); pointed tips narrowly rounded; fused claw smooth, blunt; ventrodistal claw of podomere IV stout, with sharply beveled tip.

Hemipenis heavily sclerotized, complex. Basal segment broad, subrectangular, with flaring, rounded posteroventral corner and diagonal chitinous ridge. Medial segment subcircular; seminal vesicle and base of copulatory tube located posterodorsally, at 0.81 of length. Terminal segment short, located at dorsal inner edge; lamellar, with short lobate extension above incised groove. Distal protuberances include spatulate lamella and irregular triangle connected by low ridge, thin spine, and thick hook-shaped claw. Sclerotized sleeve of copulatory tube short, stout, tapered, looped across posterior end, held in place by curved grooves on two prominences; distal part short, thin, flexible; apparently trifurcate but perhaps snarled.

Comparisons. In size, B. scaura is closest to two Australian species, B. geelongensis and B. sinusaquilensis, which also share the scoop-shaped carapace outline (shape group 1). The (decalcified) carapace of B. scaura does not display the finely punctate texture of those two species. The antennal claws of B. scaura resemble those of B. sinusaquilensis, whereas those of B. geelongensis are more pointed. Other points of similarity to B. sinusaquilensis include the three-part hinge with dentate terminal elements and serrate median element, and the enlarged proximal barbs of seta 2 of the furca.

The hemipenis of B. scaura resembles that illustrated for B. sinusaquilensis by Hartmann (1980). Similarities include the rounded, expanded posteroventral corner of the basal segment; the short, posteriorly displaced, broadly elevated copulatory tube; and the general configuration of posterodistal appendages of the medial segment. All of these posterodistal prominences are shorter and more delicate in B. scaura, however. The hemipenis of B. scaura lacks the flared, hood-like posteroventral shield of B. alcyonicola, B. angolensis, B. cratericola, and B. mocamedesensis. The heavily sclerotized posteroventral corner of the medial segment is not prolonged into a lobate or angulate prominence, as it is in B. cushmani and B. cytheraeformis.

Remarks. B. sinusaquilensis was described by Hartmann (1979, 1980) from Eagle Bay at Cape Naturalist, southwest Australia and from three localities on the warm-temperate coast of south and southeast Australia. Direct dispersal between these localities and the Hawaiian Islands is unlikely.

FIGURE 9. Bairdoppilata scaura, n. sp., all male specimen 3864M. A–B, right and left exteriors of whole animal before dissection, with soft body, food balls and genitalia; C, anterior margin of RV exterior with LV interior below, with eyelash and simple setae, selvage and flange; D, LV interior, anteroventral margin (located just below fig. C); E, LV interior, RPC at ventral indentation (bow-shaped process) just behind mouth; F, LV interior, posteroventral region (rotated 40o counterclockwise), showing RPC, simple, eyelash and plumose setae; G, dorsal region of decalcified carapace with striate and scalloped hinge, viewed from interior; H, posterior extension of fig. G, to show supplemental dentition on posterodorsal edge of RV; I–J, enlarged views of fig. G to show striate hinge, with sinusoidal ribbons and scalloped terminal extensions. Scale bar = 50 µm.