Syntomodrillia hesperia, 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 : 329-330

Syntomodrillia hesperia , new species

( Plate 170 )

Type material. Holotype 8.5 x 2.8 mm, G. Macintosh! 11 Nov 1992 (USNM 1291369); 4 paratypes: 1 spec., 6.1 x 2.4 mm, in 200 m, dredged offshore of Panama, 2010 (ANSP 464962); 1 spec., 7.6 x 2.9 mm, in 180 m, off Escudo de Veraguas I., Bocas del Toro Prov., Panama, dredged 2002 (ANSP 494997); 1 spec., 5.6 x 2.1 mm, in 201 m, off Escudo de Veraguas I., Bocas del Toro Prov., Panama (P. Stahlschmidt coll.); 1 spec., 9.1 x 2.9 mm, in 180 m, off Roatan I., Honduras, dredged 2002 (ANSP 464961).

Type locality. Off Tambor Cay, Colón Prov., Panama, on mud.

Range and habitat. Honduras (off Roatan I.); Panama (off Bocas del Toro Prov.; off Colón Prov.). Taken mostly from 180–201 m; the holotype was reported taken from 9 m.

Description. Shell very small (to 9.1 mm in total length), narrowly fusiform, glossy, with numerous ribs and a moderately long anterior canal. Whorls up to 8¾, profile flat to slightly convex, perimeters slightly below midwhorl, the last approximately 58% of total shell length; sutures impressed. Protoconch of 1½ round, translucent, rapidly expanding whorls; tip of first impressed in second. Axial sculpture of ribs that run suture-to-suture on spire whorls and to anterior fasciole on last; ribs slightly opisthocline, recurved on shoulder, and slightly sigmoid on last whorl. First teleoconch whorl with 8–9 narrow ribs, more convex than on subsequent whorls; ribs 9–10 on penultimate, and 8–10 on last whorl to varix. Ribs wider than intercostal space; crests ridged. Varix convex, higher and wider than adjacent ribs, straight, positioned about ⅓-turn from edge of outer lip. Spiral sculpture of faint spiral grooves on last 3–4 whorls, obsolete on rib crests and absent on shoulder near suture. Threads and ridges develop on anterior portion of base and are strongest on anterior fasciole. Sulcus absent; past positions of anal sinus indicated by the absence of intercostal grooves, and recurved ribs and growth striae. Outer lip flattened, with 3 or more strengthening axial folds; edge of lip from anal sinus to anterior canal forms a low arc indented at stromboid notch and slightly bent outward along the anterior canal. Anal sinus a deep notch with a round apex adjacent to suture; sides slightly divergent; inner margin of sinus flared out. Inner lip narrow, erect anteriorly, thinnest on parietal wall, and developed into a callus posteriorly at the anal sinus. Anterior canal moderately long, open, turned slightly to the right at its end when viewed ventrally, end notched asymmetrically; columella straight; fasciole with 8–9 spiral ridges. Color a light golden brown, or cream, with a broad, faint white spiral band above the suture.

Remarks. Taxonomy. Syntomodrillia hesperia , new species has all of the principal characteristics of Syntomodrillia : a small, slender, glossy shell, moderately long anterior canal, axial ribs that extend from suture-tosuture, microscopic intercostal grooves, and a narrow, not hump-like varix removed from the edge of the lip by ¼- to ⅓-turn. Variability. The five specimens have an average total length of 7.38 mm (5.6–9.1 mm) and an average W/ L ratio of 0.360. Identification. Syntomodrillia hesperia is similar to S. peggywilliamsae , new species, S. stahlschmidti , new species, S. trinidadensis , new species, and S. portoricana , new name. From S. peggywilliamsae it differs in number of protoconch whorls (1½ versus 2). From S. stahlschmidti with which it may be easily be confused because both have a long tapering last whorl, it differs in possessing a 1½-whorl protoconch, not 2½ whorls, and has an obscure central white band that is not as distinct as in S. stahlschmidti . From S. trinidadensis it differs in possessing a 1½-whorl protoconch, not 1¾ whorls and in being smaller and slimmer. From S. portoricana it differs in having fainter intercostal spiral grooves, a straighter anterior canal, a less globose protoconch, and a faint white spiral band. It lacks a dark color patch like that on the varix of S. portoricana .

Etymology. The Western Syntomodrillia , named as such because its reported localities are the western-most of known of Caribbean species ( Panama, Honduras). From the Latin adjective hesperius, feminine hesperia , meaning western.

Figures

PLATE 170. Syntomodrillia hesperia, new species. Figs. 1 – 3: holotype, Tambor Cay, Panama (USNM 1291369). 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. Figs. 4 – 7: paratypes, all ventral views. Fig. 4: off Escudo de Veraguas I., (P. Stahlschmidt coll.); Fig. 5: off Escudo de Veraguas I., (ANSP 464997); Fig. 6: off Panama (ANSP 464962); Fig. 7: off Roatan I., Honduras (ANSP 464961).