Leptadrillia histriata, 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 : 218-219

Leptadrillia histriata , new species

( Plate 107 )

Type material. Holotype 9.8 x 3.0 mm (USNM 1291352); 3 paratypes: 1 spec., 9.2 x 3.0 mm, from type locality (ANSP 464964), 1 spec., 8.6 x 2.9 mm, in 250 m, off Escudo de Veraguas I., Bocas del Toro Prov., Panama, Nov 2003 (USNM 1291353); 1 spec., 7.2 x 2.5 mm, in 250 m, off Escudo de Veraguas I. Bocas del Toro Prov., Panama, 2012 (author’s coll.).

Type locality. Gulf of Morrosquillo, Colombia, at 20– 30 m.

Range and habitat. Colombia (Gulf of Morrosquilla); Panama (off Escudo de Veraguas I.). Reported from 20–250 m, and in the case of the shallow depth, from on a gravel bottom.

Description. Shell very small (to 9.8 mm in total length), glossy, narrowly fusiform; whorls convex with impressed sutures, number up to 9¾, the last about 55% of total length, with a narrow aperture and long anterior canal. Surface of shell sculpted by regularly spaced axial ribs, very slightly convex. Protoconch of 2 smooth, round translucent whorls, the second somewhat bulbous. Axial sculpture of narrow, slightly curved ribs with ridged crests that run from suture-to-suture on spire whorls, to anterior fasciole on last where they are slightly sigmoidal; ribs wider than their intercostal spaces, number 11–15 on penultimate, 7–12 to varix on last whorl to varix. Ribs deeply impressed at suture. Vari x wider than preceding ribs, straight not sigmoidal, and round-crested; positioned approximately ¼-turn from lip edge. Spiral sculpture absent except for 6–10 spiral ridges on anterior fasciole. Sulcus absent; recurved ribs on shoulder echo previous positions of anal sinus. Outer lip thin, partially translucent, edge smooth, strengthened from varix to lip edge by axial folds curved parallel to edge of outer lip, which is a low arc extending from anal sinus to stromboid notch. Stromboid notch very shallow. Anal sinus deep, apex round, sides straight, offset slightly from shell axis by parietal callus; inner edge of sinus slightly flared. Inner lip narrow, margined, erect on anterior canal, formed into a parietal callus posteriorly; successive layers of deposition visible on lip’s edge. Anterior canal long, open, end slightly turned right when viewed ventrally; unnotched. Color light beige with a white anterior canal, and a light golden brown patch present on ventral side of holotype’s varix but not on all paratypes.

Remarks. Taxonomy. Leptadrillia histriata has all of the distinguishing characteristics of Leptadrillia : a spindle-shaped shell with a narrow aperture and long anterior canal, ribs that extend from suture-to-suture without a sulcus, and no spiral sculpture except on the anterior fasciole. Variability. The average total length of four specimens is 8.70 mm (7.2–9.8 mm), and their W/ L ratio is 0.329. Little variation is seen in the specimens examined. Identification. Leptadrillia histriata is similar to L. splendida Bartsch, 1934 (9.2 mm total length), L. violacea , new species (8.60 mm average total length), L. lizae , new species (8.44 mm average total length), and L. luciae , new species (9.54 mm average total length). Leptadrillia loria, Bartsch, 1934 , is smaller and less likely to be mistaken for this species (6.8 mm total length). L. histriata differs from L. splendida in possessing more ribs (11–15 versus 10 on the penultimate whorl) that are straighter, and in having ridged not round-crested ribs. From L. violacea it differs in possessing more ribs (11–15 versus 9–10 on the penultimate whorl) that have ridged crests, not rounded ones. It also lacks the violet-colored protoconch and early whorls characteristic of some L. violacea . From L. lizae it differs in possessing less convex whorls and generally more ribs (11–15 versus 12 on the penultimate whorl). From L. luciae it differs in possessing more ribs (11–15 versus 9 on the penultimate whorl) and lacking the light golden brown band on the whorls’ shoulder.

Etymology. The Fluted Leptadrillia . From the Latin adjective histriatus (feminine histriata ) meaning fluted or grooved. The spindly shell with regularly spaced, even ribs separated by V-shaped grooves brings to mind a fluted pole.

Figures

PLATE 107. Leptadrillia histriata, new species. Figs. 1 – 3: holotype, Gulf of Morrisquillo, Colombia (USNM 1291352). Fig. 1: ventral, lateral & dorsal views; Fig. 2: apical view, V = varix, L = edge of outer lip; Fig. 3: enlarged view of the protoconch (not to scale). Figs. 4 – 6: paratypes. Figs. 4 – 5: off Escudo de Veraguas I., Panama (author’s coll. & USNM 1291353, respectively); Fig. 6: Gulf of Morrosquillo, Colombia (ANSP 464964).