Syntomodrillia triangulos, 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 : 346-348

Syntomodrillia triangulos , new species

( Plate 180 )

Type material. Holotype 6.9 x 2.9 mm (ANSP 465242); 7 paratypes: 6.5 x 2.5 mm (EFG 26617), 6.8 x 2.6, 6.2 x 2.5, 7.7 x 2.9, 7.0 x 2.8, 7.0 x 2.8 & 6.4 x 2.5 mm (EFG 26618), all from the type locality, E. García! aboard R/V Pelican, 10 Jun 2005.

Type locality. W of Triángulos Reef, Campeche Bay, Mexico, 20°51.16'N, 092°26.28'W and 20°52.40'N, 92°24.83'W, in 77– 94 m.

Range and habitat. Known only from the type locality.

Description. Shell very small (to 7.7 mm total length), fusiform, surface glossy, translucent, with up to 8 convex whorls with peripheries a little below mid-whorl; last whorl approximately 59% of total length. Whorls sculpted with axial ribs. Aperture narrowly oval, anal notch near suture posteriorly and moderately long canal anteriorly. Protoconch of 1½–1¾ smooth round whorls. Axial sculpture of broad, curved ribs that run suture-tosuture on spire whorls and evanesce at anterior fasciole on last; slightly recurved and lower on shoulders, sigmoidal on last whorl. Ribs narrow, crests round; intercostal space greater than their width; number 9–11 on penultimate and 6–8 on last whorl to varix. Growth striae microscopic, most visible on last whorl. Varix convex, rib-like, straight, only a little higher and wider than adjacent ribs; positioned about ⅓-turn from edge of outer lip. Spiral sculpture of very faint spirals between ribs below shoulder of last whorl and 7 threads on the anterior fasciole. Sulcus absent; past positions of the anal sinus marked by lower and slightly recurved ribs on shoulder just below suture of last 2 whorls. Outer lip slightly flattened from the base of varix; surface with coarse growth striae and 2 weak axial folds near lip’s edge; lip edge traces a curve from anal sinus to anterior canal; stromboid notch at the beginning of the anterior canal. Anal sinus a deep notch adjacent to suture, outer side divergent and congruent with edge of outer lip. Inner lip narrow, emarginated, erect and thick on columella anteriorly, recumbent and thinner on parietal wall, and forming a weak lobe on parietal side of anal sinus posteriorly. Anterior canal moderately long, open, angled slightly to the right when viewed ventrally; unnotched; fasciole not swollen. Color white to off-white.

Remarks. Taxonomy. Syntomodrillia triangulos possesses the characteristics of the genus: small size, a fusiform shell sculpted with ribs extending from suture-to-suture and to the anterior fasciole on the last whorl, and a varix about ⅓-whorl from the edge of the outer lip. Variability. Eight specimens have an average total length of 6.81 mm (6.2–7.7 mm), and an average W/ L ratio of 0.395. Identification. Syntomodrillia triangulos is similar to Leptadrillia loria Bartsch, 1934 , S. socolatea , new species, S. mellea , new species, and S. floridana , new species. From L. loria it differs in having a shorter anterior canal, a stouter, not spindly shell, and faint spirals on the shell base before the anterior fasciole, which are absent on L. loria . From S. socolatea it differs in possessing more convex whorls, and a different color—white to off-white, not a light golden to chocolate brown color. From S. mellea it differs in being somewhat larger (6.81 versus 5.55 mm), in possessing slightly more convex whorls, and in being a different color—solid white to off-white, not light golden brown with whitish shell base and varix. From S. floridana it differs in possessing slightly more convex whorls, fewer axial ribs (9–11 versus 12), and a protoconch with fewer whorls (1½ versus 2).

Etymology. The Triángulos Reef Syntomodrillia , named after the reef on Campeche Bank near where the type specimens were taken.

Figures

PLATE 180. Syntomodrillia triangulos, new species. Upper Panel. Figs. 1 – 3: holotype, W of Triángulos Reef, Campeche Bay, Mexico (ANSP 465242). 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. Lower panel. Figs. 4 – 9: paratypes, W of Triángulos Reef, Campeche Bay, Mexico (EFG 26618).