Syntomodrillia portoricana

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 : 340-342

Syntomodrillia portoricana , new name for Syntomodrillia tantula Bartsch, 1934

( Plate 176 )

Syntomodrillia portoricana , new name for Syntomodrillia tantula Bartsch, 1934: 28 –29, pl. 8, figs. 2, 3, 6, non Syntomodrillia tantula (Conrad, 1848a:284; 1848b: 115). Conrad’s name is a senior secondary homonym (ICZN 2000 Article 53.3) of a fossil of the Oligocene of Vicksburg, Miss.

Splendrillia (Syntomodrillia) tantula (Bartsch, 1934) : Powell (1966: 84); Abbott (1974: 275, species 3112). Splendrillia tantula (Bartsch, 1934) : Rios (1975: 134, pl. 40, fig. 606); Williams (2005: species 1585).

Not this species, or unconfirmed extralimital reports.

Splendrillia (Splendrillia) tantula (Bartsch, 1934) : Rios (1975: 134, pl. 40, fig. 606 [ Brazil: Amapá]). Splendrillia (Syntomodrillia) tantula (Bartsch, 1934) : Rios (1985: 140; pl. 48, fig. 646 [ Brazil: Amapá]); Rios (1994: 163; pl. 54, fig. 738 [ Brazil: Amapá]); Rios (2009: 315, fig. 802 [ Brazil: Amapá]).

Type material. Holotype 7.0 x 2.5 mm (7.1 x 2.8 according to Bartsch) (USNM 430164). The paratype from the type locality was not examined (USNM 430854).

Type locality. R/V Caroline Sta. 16, off the N coast of Puerto Rico near Morro Castle light and Punta Salinas, between 18°29'40"N, 66°08'30"W and 18°31'00"N, 66°10'15"W, in 38–95 fms [69–174 m].

Other material examined. An additional eight specimens were examined: 2 spec., 7.8 x 2.9 & 7.4 x 2.7 mm, in 5 m, Boca de Inferno, Jobos, Puerto Rico (USNM 900153); 2 spec., 6.9 x 2.7 & 7.2 x 2.5 mm in 5 m, Boca de Inferno, Jobos, Puerto Rico (author’s coll.); 2 spec., 8.6 x 3.1 & 8.3 x 2.9 mm, off Mayaguez, Puerto Rico, G.L Warmke! 1952 (ANSP 253140); 1 spec., 9.4 x 3.2 mm, in 12 m, off docks, Mayaguez Puerto Rico, G.L. Warmke! 16 Nov 1952 (ANSP 314085).

Range and habitat. Puerto Rico (N coast). Reported from 5– 125 m.

Description. Shell very small (to 9.4 mm total length), narrowly fusiform, glossy, whorls slightly convex, rib peripheries below mid-whorl; whorls to about 9¾, the last approximately 59% of total length. Sculptured with numerous ribs; aperture oval and short. Protoconch of approximately 1½ round, rapidly expanding, translucent whorls, tip of first partially impressed in second; protoconch globular, but not exceeding diameter of first teleoconch whorl. Axial sculpture of broad ribs suture-to-suture on spire whorls, to fasciole on last. Ribs slightly opisthocline, recurved in sulcus; 8–11 on penultimate, 5–10 on last whorl to varix. Ribs about as wide as intercostal space; rib crests ridged. Vari x heavy, straight, not oblique like adjacent ribs, located approximately ⅓-turn from edge of outer lip. Spiral sculpture of deep grooves appearing as threads between the ribs (obsolete on rib crests), absent in sulcus but present on all whorls; threads become stronger on shell base then become ridges just before and on anterior fasciole, 9–10 on fasciole. Sulcus absent; ribs and growth striae are curved just below suture to reflect the outline of anal sinus, spiral grooves absent. Outer lip thin, translucent, flattened outward from the varix, with one or more strengthening axial folds; edge of lip from anal sinus to anterior canal forms a low arc; slightly indented at stromboid notch and flexed outward along canal. Anal sinus a deep U-shaped notch on whorl shoulder near suture, sides parallel; outer lip and sinus inner margin flared out; sinus angled away from shell axis. Inner lip recumbent, moderately wide, margined, thickest anteriorly, thin on parietal wall; developed into an elongate lobe posteriorly along one side of the anal sinus on the roof of the aperture. Anterior canal moderately long, open, bent slightly to the right at its end when viewed ventrally; unnotched; columella straight; fasciole not swollen. Color pale wax yellow (holotype); what are possibly fresher specimens are a golden brown, the shell base and outer lip paler. A darker golden brown patch is present on the ventral side of the varix.

Remarks. Nomenclature. An entirely different species, Pleurotoma (Clavatula) tantula Conrad, 1848a: 284 (Oligocene, Vicksburg, Mississippi fossil) was placed in Syntomodrillia by Mansfield (1940: 206, pl. 27, fig. 15), a combination recently used by MacNeil & Dockery (1984: 201, pl. 36, figs. 13–15, 18, 19). As such, Bartsch’s species becomes a junior secondary homonym, as Conrad’s name has priority. To the best of this author’s knowledge, there are no available synonyms for Bartsch’s species, so the new name is proposed herein. Taxonomy. Syntomodrillia portoricana has all of the characteristics described by Woodring for the genus: small, glossy, axial ribs numerous, from suture-to-suture, microscopic threads between the ribs, and a moderately long anterior canal.

Variability. The average total length of eight specimens is 7.83 mm (6.9–9.4 mm); their average W/ L ratio is 0.360. Identification. Some of the small, glossy, spindle-shaped species in the genus Syntomodrillia may be difficult to distinguish. Syntomodrillia portoricana is similar to S. carolinae Bartsch, 1934 , S. cookei (E.A. Smith, 1888) , and S. hesperia , new species. From S. carolinae it differs in having whorl peripheries below mid-whorl, not generally mid-whorl, a less translucent shell, fewer and broader ribs (8–11 versus 10–14 on the penultimate whorl), an anterior canal bent to the right when viewed ventrally, not straight, and more spiral threads on the anterior canal (9– 10 versus 3–5). From S. cookei it differs in having broader ribs that are not as oblique, a mostly opaque shell, not translucent as in S. cookei , and a different coloration. From S. hesperia it differs in being stockier, having opisthocline, not straight ribs, and in lacking a diffuse white central band.

Etymology. The Puerto Rican Syntomodrillia . The name recognizes the country of the type locality where all specimens have been found to date.

Figures

PLATE 176. Syntomodrillia portoricana, new name. Upper panel. Figs. 1 – 3: holotype, off N coast of Puerto Rico (USNM 430164). Fig. 1: ventral, lateral & dorsal views; Fig. 2: enlarged view of protoconch (not to scale); and Fig. 3: apical view, V = varix, L = edge of outer lip. Lower panel. Figs. 4, 7 – 8: Jobos, Puerto Rico (author’s coll.): Figs. 4, 7: ventral view; Fig. 8: enlarged view of protoconch (not to scale); Figs. 5 – 6: Jobos, Puerto Rico (USNM 900153); Figs. 9, 11: off Mayaguez, Puerto Rico (ANSP 253140); Fig. 10: Mayaguez, Puerto Rico (ANSP 314085).