Splendrillia subtilis, 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 : 310-312

Splendrillia subtilis , new species

( Plate 160 )

Type material. Holotype 9.1 x 3.4 mm, T. McCleery! Nov 2005, ex coll. P. Stahlschmidt (SMF 336442). No paratypes.

Type locality. Rosario I., Cartagena Dept., Colombia, in 30– 50 m.

Range and habitat. Known only from the holotype.

Description. Shell small (to 9.1 mm total length), narrowly fusiform, truncated anteriorly, thin, surface glossy; whorls convex, number 7¾, the last whorl 56% of total shell length; predominant sculptural elements are ribs; aperture narrow; anterior canal short. Protoconch of 2 smooth round whorls. Axial sculpture of bold slightly opisthocline ribs that run from suture-to-suture on spire whorls, evanesce on base before anterior fasciole, and tending to aligned from whorl to whorl. Ribs round-crested, lower, narrower, and slightly reduced on shoulder, number 6 on penultimate, 4 on last whorl to varix; intercostal space wider than ribs. Growth striae strong. Varix broad and wide, hump-like, approximately ⅓-turn from edge of outer lip. Spiral sculpture of fine threads on anterior fasciole. Shell surface microsculpture consisting of a repeating pattern of very fine threads or grooves with groups of finer threads or grooves between. This pattern is mostly obscured by strong growth striae. Sulcus a nearly flat band adjacent to suture with growth striae and obsolete or nearly obsolete slightly recurved ribs, about ⅓-height of spire whorls. Outer lip thin, flattened from varix to lip’s edge, with no significant axial folds but with heavy growth striae developed into ridges; edge of lip forms an arc from anal sinus to anterior canal; stromboid notch absent. Anal sinus incompletely formed; is a shallow U-shaped notch next to the suture in the type specimen,. Inner lip narrow, unemarginate except for the anterior end, which is erect. No parietal lobe is present, likely because of the incomplete development of the type. Anterior canal short, open, unnotched; fasciole not swollen but with fine spiral threads. Color off white with a wide spiral band mid-whorl, interrupted by ribs adapically, continuous elsewhere; darker in intercostal spaces. A light patch of golden brown extends along the ventral face of the varix.

Remarks. Taxonomy. Splendrillia subtilis has distinguishing characteristics of the genus: a glossy-smooth shell with a bare sulcus, hump-like varix positioned about ⅓-turn from the edge of outer lip with a dark color patch, and a short, open anterior canal. Identification. Splentrillia subtilis is similar to S. abdita , new species but has a more angular last whorl, and is a different color. It is similar to Fenimorea contracta , new species but is smaller (9.1 versus 15.3 mm in total length), has more ribs (7 versus 5 on the penultimate whorl), a broader shape (W/ L ratio of 0.374 versus 0.353), a plain sulcus without ribs, which is characteristic of Splendrillia , and a different color pattern: an unbroken brown spiral band with darker intercostal patches. Brown patches are confined to rib interspaces on F. contracta . From Fenimorea petiti Tippett, 1995 it differs in being smaller (9.1 versus 23.6 mm in total length, an average length for F. petiti ), in possessing a mid-whorl color band broken by ribs and varying in shade, not continuous and uniform in shade as in F. petiti , and its color band darker than usually seen in F. petiti . Both F. contracta and F. petiti have shell surface microsculpture characteristic of Fenimorea , which is unlike that of Splendrillia .

The single specimen merits description as new because it is morphologically unlike its congeners, as described above (see Plate 163 ). Also, it is one of only two Splendrillia known from the southwest Caribbean. The other, S. panamensis , new species, is larger (up to 14.5 versus 9.1 mm total length) and has more ribs (8–10 versus 6 on the penultimate whorl).

Etymology. The Fine-spun Splendrillia . From the Latin adjective subtilis meaning fine, delicate, a reference to both its delicate shell and very fine spiral microsculpture.

Figures

PLATE 160. Splendrillia subtilis, new species. Figs. 1 – 3: holotype, Rosario I., Cartagena Prov., Colombia (SMF 336442). Fig. 1: ventral, lateral, and dorsal views; Fig. 2: enlarged view of protoconch; Fig. 3: apical view, V = varix, L = edge of outer lip.

PLATE 163. Splendrillia spp. map and lineup: other species. Fig. 1. Map of approximate known localities. Fig. 2. Holotype, 7.6 x 2.5 mm, S. stellae, new species (ANSP 465011). Fig. 3. Holotype, 9.1 x 3.4 mm, S. subtilis, new species (SMF 336442). Fig. 4. Holotype, 18.5 x 6.6 mm S. grandis, new species (USNM 1291361). Fig. 5. Holotype, 14.5 x 5.5 mm, S. panamensis, new species (USNM 900143). Fig. 6. Holotype, 13.8 x 5.0 mm, S. flavopunctata, new species (ANSP 353508). Fig. 7. Holotype, 12.4 x 4.8 mm, S. compta, new species (MZSP 122075). Fig. 8. Holotype, 10.2 x 4.0 mm, S. alticostata, new species (MNHN IM- 2012 - 28011).