Syntomodrillia curacaoensis, 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 : 325-326

Syntomodrillia curacaoensis , new species

( Plate 167 )

Type material. Holotype 7.9 x 3.0, M.G. Harasewych! aboard submersible Curasub , 24 May 2012 (USNM 1199830); 1 paratype: 6.8 x 2.6 mm, from type lot (USNM 1287764).

Type locality. Off Sea Aquarium, Bapor Kibra, Willemstad, Curaçao, Netherlands Antilles, 12°04.87'N, 68°53.75'W, in glass bottles collected at 288 m.

Range and habitat. Known only from type locality.

Description. Shell very small (to 7.9 mm in total length), glossy, partially translucent, broadly fusiform; with convex whorls, sutures appressed; whorls number about 8, the last approximately 58% of the total length; aperture short and relatively wide. Protoconch of 2 translucent, relatively large, smooth round whorls, the first not immersed in the second. Axial sculpture of slightly opisthocline ribs suture-to-suture on spire whorls, to anterior fasciole on last. Ribs are recurved on the shoulder, have their peripheries slightly below mid-whorl, and number 10–11 on the penultimate, 7 on the last whorl to the varix. Varix like a swollen rib, about ⅓-turn from edge of outer lip. Spiral sculpture of 6 ridges on the anterior fasciole. Microsculpture of faint intercostal grooves on last and penultimate whorls. Sulcus absent. Prior positions of the anal sinus indicated by recurved ribs and growth striae, and absence of intercostal spiral grooves. Outer lip thin, translucent, somewhat swollen bubble-like, with two thin, strengthening axial folds near the edge. Edge of lip forms a low arc from anal sinus to anterior canal; stromboid notch shallow. Anal sinus a deep notch with a round apex adjacent to suture on shoulder, sides slightly convergent; inner rim flared out. Inner lip emarginated, narrow and erect on end of anterior canal, recumbent elsewhere, widest on upper canal then narrows to a weak parietal lobe on parietal lobe. Anterior canal moderately long, wide, open, slightly twisted to the right when viewed ventrally, notched; anterior fasciole not swollen. Color translucent white with pale pinkish-brown band on whorl shoulders and below suture line on last whorl. Patch of color on shoulder and ventral side of varix is light golden brown.

Remarks. Taxonomy. Syntomodrillia curacaoensis possesses the combination of characters that are unique to the genus: a small glossy shell, fusiform, sculpted with ribs extending from suture-to-suture and to the anterior fasciole on the last whorl, a short open aperture, and a varix about ⅓-turn from the edge of the outer lip. Identification. Syntomodrillia curacaoensis is similar to seven of the smaller members of the genus: S. triangulos , new species, S. mellea , new species, S. harasewychi , new species, S. pusilla , new species, S. floridana , new species, S. cookei (E.A. Smith 1888) , and S. woodringi . From S. triangulos it differs in number of protoconch whorls (2 versus 1½) and color (pale pinkish-brown bands versus all- to off-white). It is larger than S. mellea (6.8– 7.9 versus 5.0– 6.4 mm in total length), differs in number of protoconch whorls (2 not 1¾), and differs in color (white with pale pinkish-brown band versus all golden brown). It has a broader shell profile and shorter anterior canal than S. harasewychi (average W/L = 0.381 versus 0.357), has weaker intercostal spiral grooves, has more convex whorls, and is a different color (white with pale pinkish brown bands versus all-white). It is larger than S. pusilla (6.8–7.9 versus 5.1 mm in total length), has weaker intercostal grooves, and differs in number of protoconch whorls (2 not 1½). From S. floridana it differs in whorl profile (more convex whorls) and color (pale pinkishbrown band versus all-white or pale yellow-brown). From S. cookei it differs in number of protoconch whorls (2 versus 1½), in the taper of the last whorl, which is slightly more angular, and color (white with a pale pinkishbrown band versus a monochromatic white, pink, light orange-brown, or lavender). It is somewhat smaller than S. woodringi (6.8–7.9 versus 7.2–9.7 mm in total length), has a protoconch with slightly less whorls (2 versus 2–2½ whorls), weaker intercostal grooves, a shorter anterior canal, and a different color (white with pale pinkish-brown band versus all-white).

Although the field of very similar species of Syntomodrillia is crowded, the small sample of S. curacaoensis differs in the combination of characters that have been found to be consistent within species of the genus-group, and so merits description as a separate species.

Etymology. The Curaçao Syntomodrillia ; named after the country of the type locality.

Figures

PLATE 167. Syntomodrillia curacaoensis, new species. Figs. 1 – 3: types, off Sea Aquarium, Bapor Kibra, Willemstad, Curaçao. Fig. 1: holotype, ventral, lateral & dorsal views (USNM 1199830); Figs. 2 – 3: paratype, ventral view (USNM 1287764) & enlarged view of protoconch (not to scale), respectively.