Syntomodrillia trinidadensis, 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 : 348-349

Syntomodrillia trinidadensis , new species

( Plate 181 )

Type material. Holotype 11.3 x 4.0 mm, G. Mackintosh! 27 Jan 2006 (USNM 1291370). Type locality. Scotland Bay, Trinidad I., Trinidad and Tobago, in 15– 18 m. Range and habitat. Known only from the holotype.

Description. Shell small (11.3 mm total length), fusiform, glossy, with numerous ribs and a moderately long anterior canal. 9¼ flat to slightly convex whorls, sutures impressed; whorl perimeters slightly below mid-whorl, the last 58% of total shell length. Aperture widely oval, almost round. Protoconch of 1¾ round, translucent, rapidly expanding whorls; tip of first partially immersed in second such that the protoconch appears dome-shaped. Axial sculpture of broad ribs that run suture-to-suture on spire whorls and to fasciole on last; ribs bowed on spire whorls, little changed in sulcus, becoming narrower and opisthocline on shell base such that ribs appear sigmoid overall on last whorl. First teleoconch whorl with 8 narrow ribs, more convex than on subsequent whorls; ribs 11 on penultimate, and 8 on last whorl to varix. Ribs wider than their intercostal space; crests ridged. Vari x convex, higher and wider than adjacent ribs, straight. Spiral sculpture of faint spiral grooves on anterior half of all whorls, obsolete on rib crests and absent in sulcus; 3–4 grooves are deeper and ridge-like adjacent to anterior fasciole. Sulcus absent, previous positions of anal sinus indicated, especially on last whorl, by a slight additional curvature of the ribs, slightly excavated on ventral side, by stronger, curved growth striae, and absence of spiral grooves. Outer lip thin, flattened, with 4 axial folds of irregular width and spacing; lip edge a low arc between anal sinus and stromboid notch, which is shallow and broad. Anal sinus a deep notch with a round apex; sides slightly divergent, the outer side extending beyond the parietal side of the notch. Inner lip detached, erect anteriorly, thinnest on parietal wall, and formed into a weak callus on the inner side of the anal sinus, which is positioned over the roof of the aperture. Anterior canal moderately long, open, turned to the right when viewed ventrally, deeply notched; columella straight; fasciole with 9 spiral ridges. Color a grayish base with indistinct light golden brown bands at the suture and just below mid-whorl.

Remarks. Taxonomy. Syntomodrillia trinidadensis has all of the principal characteristics of Syntomodrillia : a small, slender glossy shell with a moderately long anterior canal, axial ribs that extend from suture-to-suture, microscopic intercostal grooves, and a narrow, not hump-like, varix positioned approximately ⅓-turn from outer lip edge. Identification. Syntomodrillia trinidadensis is similar to three other species from the southern Caribbean that possess an asymmetrical notch at the end of the anterior canal: S. hesperia , new species, S. stahlschmidti , new species, and S. peggywilliamsae , new species. It differs from all three in size (11.3 versus 8.9 mm, the largest), shape of their apertures (widely oval versus elongate), and color (a grayish base with indistinct golden brown bands at the suture and just below mid-whorl versus a light golden brown with a very faint to distinct white mid-whorl band). It also differs in number of protoconch whorls (1¾ versus 1½, 2½, and 2, respectively). These distinctions indicate difference at the species level. Their separate island localities ( Trinidad I., Tambor Cay, Panama, Bahia Concha, Colombia, and Tobago I., for S. trinidadensis , S. hesperia , S. stahlschmidti , and S. peggywilliamsae , respectively) suggests an isolating mechanism.

Etymology. The Trinidad Syntomodrillia , named for the country of the type locality.

Figures

PLATE 181. Syntomodrillia trinidadensis, new species. Figs. 1 – 3: holotype, Scotland Bay, Trinidad I. (USNM 1291370). Fig. 1: ventral, lateral & dorsal views; Fig. 2: enlarged views of protoconch (not to scale); Fig. 3: apical view, V = varix, L = edge of outer lip.