Splendrillia grandis, 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 : 299-300

Splendrillia grandis , new species

( Plate 152 )

Type material. Holotype 18.5 x 6.6 mm (USNM 1291361); 1 paratype: 17.4 x 6.5 mm, from the type locality (EFG 26218). Both types: E. García! aboard R/V Pelican, 13 Jun 2005, ex E. García coll.

Type locality. Campeche Bank off Yucatan, Mexico, 21°51.32′N, 092°03.68′W, in 66– 68 m.

Range and habitat. Known only from the type locality. Reported from on a substrate mix of mud and shell.

Description. Shell small sized (to 18.5 mm), fusiform, truncated anteriorly; whorls strongly convex, number up to 9¾, the last whorl approximately 56% of the total length. Shell surface glossy, sculptured with coarse growth striae and strong ribs. Aperture wide, narrowing to a short anterior canal. Protoconch of 2 smooth round whorls. Axial sculpture of strong, slightly opisthocline ribs, run from sulcus to succeeding whorl’s suture, evanesce on shell base close to anterior fasciole, 10–11 on penultimate, 8 to varix on last whorl with interspaces 1– 2x rib width. Periphery of ribs a little below mid-whorl. Growth striae present; heaviest on last whorl where they impart a coarse surface to shell surface. Varix large, positioned about ¼-whorl from edge of outer lip. Spiral sculpture minimal, faint spiral threads sparse on shell base, 4–5 stronger threads on anterior fasciole. Sulcus concave, about ⅓-whorl height; ribs nearly obsolete, lower, narrower, and curved, reflecting the outline of anal sulcus. Outer lip plain but thickened by closely spaced folds (up to 4); forms a low nearly flat arc from the anal sinus to the anterior canal; with a slight indentation marking the stromboid notch; inflection of outer rib along canal lacking. Anal sinus deeply notched, parietal side attached to suture behind the callus. Inner lip thin and unemarginate on parietal wall, margined anteriorly, formed into a low callus posteriorly. Anterior canal hardly defined, end notched; fasciole slightly swollen; with 4–5 spiral threads. Color a light caramel overall, with a mid-whorl band of dark caramel broken up by the ribs and a narrower faint white band above it; varix shoulder with a patch of dark caramel; aperture and columella white.

Remarks. Taxonomy. Splendrillia grandis differs somewhat from the typical Splendrillia in that the axial ribs are not completely absent in the sulcus, but lower and a little narrower vestiges are present, similar to what is typically found in some Cerodrillia . It also has coarser growth striae, though not as coarse as seen in S. bahamasensis , new species. Splendrillia grandis has the typical anal sinus where the outer lip joins the suture behind the parietal callus; the typical form of the outer lip that sweeps in an unbroken arc to the end of the anterior canal, and a varix positioned well behind the anal sinus. Variability. The two types are unlikely to exhibit the full range of variability of this species. Their average length is 17.95 mm (17.4–18.5 mm) and their average W/ L ratio is 0.365. Only slight variation in color and size is exhibited by the two specimens. Identification. Splendrillia grandis is similar in appearance to S. interpunctata (E.A. Smith, 1882) , S. bahamasensis , new species, S. panamensis , new species, and Fenimorea abscondita , new species. It differs from S. interpunctata in being larger (examined specimens up to 18.5 versus 16.5 mm in total length for S. interpunctata ), and having less angled ribs. From S. bahamasensis it differs in having much weaker growth striae and more angle shoulders. From S. panamensis it differs in being larger (examined specimens up to 18.5 versus 14.5 mm in total length), in possessing more opisthocline ribs, and a different color. From F. abscondita it differs in being smaller (measured specimens up to 18.5 versus 35.8 mm total length for F. abscondita ), in lacking the deeper spiral grooves, and in having a less distinct spiral color band.

The size, locality, and distiveness from similar species of the two specimens that form the basis of this taxon, as described above, merit its description. It is the only species of Splendrillia observed from the Gulf of Mexico and thus of interest from the perspective the overall distribution of the genus-group.

Etymology. The Grand Splendrillia , so named because it is the largest of all the Splendrillia . The minor epithet is from the Latin adjective grandis , meaning large, great, or grand.

Figures

PLATE 152. Splendrillia grandis, new species. Figs. 1 – 3: Holotype, Campeche Bank off Yucatan, Mexico (USNM 1291361). Fig. 1: ventral, lateral, and 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 from type locality (EFG 26218).