Splendrillia alticostata, Fallon, Phillip J., 2016

Fallon, Phillip J., 2016, Taxonomic review of tropical western Atlantic shallow water Drilliidae (Mollusca: Gastropoda: Conoidea) including descriptions of 100 new species, Zootaxa 4090 (1), pp. 1-363 : 282-283

Splendrillia alticostata , new species

( Plate 143 )

Type material. Holotype 10.2 x 4.0 mm, 26 May 2012 (MNHN IM-2012-28011); 2 paratypes: 1 juvenile spec., 4.2 x 2.2 mm, from same lot as holotype (MNHN IM-2000-31083); and 1 spec., 11.5 x 4.2 mm, from harbor dredgings, Oranjestad, Aruba, Netherlands Antilles (ANSP 349131).

Type locality. Petite-Terre, Guadeloupe, 16°09.7'N, 61°07.7'W, in 15 m (KARUBENTHOS 2012 Sta. GB31).

Other material examined. One additional specimen was examined: 9.6 x 3.9 mm, submersible Curasub Sta. 1, in 130–168 m, off Sea Aquarium, Bapor Kibra, Willemstad, Curaçao, 12°04.87'N, 68°53.75'W, M.G. Harasewych! 23 May 2012 (USNM 1199832).

Range and habitat. Guadeloupe (Petite-Terre); Netherlands Antilles ( Aruba; Curaçao). The type specimens were collected empty, one in beach sand dredge samples, and the other from 15 m depth. The shell collected at 130–168 m off Curaçao may have been transported from shallower water; there is a steep drop-off in the area. It is likely that the species inhabits shallow water.

Description. Shell small (to 11.5 mm total shell length), fusiform, truncated anteriorly, glossy, with a total of about 8¼ markedly convex whorls, the last approximately 60% of total length. Suture appressed, undulates over axial ribs of preceding whorl. Aperture a narrow oval. Protoconch of 1⅞ smooth round whorls, the first not immersed. Axial sculpture of high narrow ribs that run from suture-to-suture on first 3 teleoconch whorls, to sulcus on remaining whorls. Ribs lower in sulcal region on first whorls, mound-like, cord-like trace, or obsolete in sulcus of later whorls. Ribs almost wing-like at shoulder, slightly opisthocline, and where present in sulcus curved such that the entire rib appears slightly sigmoid: 9 on penultimate, 6 on last whorl to varix. Ribs evanesce on shell base below whorl periphery, are mostly absent in sulcus. Growth striae present, coarsest on dorsum of last whorl. Varix convex, higher than nearby ribs, hump-like, positioned ¼–⅓-turn from the edge of the outer lip. Spiral sculpture of about 8 fine, microscopic grooves or threads on shell base and 5 stronger ridges on anterior fasciole. Sulcus narrow, with lower ribs in early whorls where ribs extend to suture, mostly obsolete in following whorls but some ribs extend to suture as low cords, curved reflecting the outline of the anal sulcus. Outer lip mostly missing on mature types. Anal sinus a shallow notch remains that joins the suture behind a low parietal lobe. Anterior half of sinus missing on types. Inner lip thin, unemarginate; erect at anterior end of canal; with a low parietal lobe posteriorly. Anterior canal well defined, short, straight, open; fasciole not swollen. Color white, with a goldenyellow color patch on shoulder or leading (ventral) side of the varix.

Remarks. Taxonomy. Splendrillia alticostata has all the distinctive features of Splendrillia : an anal sinus that joins the suture behind the parietal lobe, ribs that are mostly absent in the sulcus, a hump-like varix, and microsculpture of faint threads and ridges confined to the shell base and fasciole. This species is unique with its high, narrow ribs. Variability. The average total length of three non-juvenile specimens is 10.43 mm (9.6–11.5 mm), and average W/ L ratio of 0.388. Identification. Splendrillia alticostata is very similar in appearance to S. interpunctata (E.A. Smith, 1882) and S. panamensis , new species. From both species it differs in possessing higher and narrower ribs with more angular shoulders. From S. panamensis it also differs in lacking a spout-like anal sinus and in possessing a golden-yellow patch on the varix. From S. interpunctata it also differs in having longer, less oblique ribs, a longer, and more tapered last whorl.

Etymology. The High-ribbed Splendrillia , named for its unusual rib form. Derived from the Latin adjective altus, meaning high, the combining form being alti-, and the Latin adjective costatus, meaning ribbed, costata the feminine form.

Figures

PLATE 143. Splendrillia alticostata, new species. Figs. 1 – 3: holotype, Petite-Terre, Guadeloupe (MNHN IM- 2012 - 28011). Fig. 1: ventral, lateral & dorsal views; Fig. 2: enlarged view of protoconch (not to scale); Fig. 3: apical view, V = varix, L = edge of outer lip. Fig. 4: paratype, Petite-Terre, Guadeloupe (MNHN IM- 2000 - 31083); Fig. 5: paratype, Aruba, Netherlands Antilles (ANSP 349131); Fig. 6: Curaçao, Netherlands Antilles (USNM 1199832).