Syntomodrillia floridana, 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 : 326-327

Syntomodrillia floridana , new species

( Plate 168 )

Type material. Holotype 7.8 x 2.7 mm, J. Moore! (USNM 900288); 1 paratype 7.3 x 2.5 mm, in 55 m, W of Tampa, Hillsborough Co., W Florida (ANSP 337391).

Type locality. Off W Florida, Gulf of Mexico.

Range and habitat. Off W Florida in Gulf of Mexico. No depth was reported for the holotype; the paratype was reported from 55 m.

Description. Shell very small (7.8 mm in total length), glossy, partially translucent, fusiform; with weakly convex, nearly flat-sided whorls with impressed sutures. Whorls number about 8½, the last whorl approximately 56% of the total length; last whorl somewhat pinched at canal, so it appears round, not tapered. Aperture narrowly oval, only a little wider than the anal sinus and anterior canal. Protoconch paucispiral, of 2 translucent, smooth round whorls. Axial sculpture of ribs suture-to-suture on spire whorls, to anterior fasciole on last. Ribs rather straight on spire whorls, and on last, recurved on shoulder then curved below, appearing sigmoid overall; ribs number 12 on the penultimate and 8 on the last whorl to the varix. Varix like a swollen rib, but straight not sigmoid, about ¼–⅓-turn from edge of outer lip. Spiral sculpture of ridges on the anterior fasciole. Shell surface microsculpture principally of heavy growth striae that may mask very fine intercostal grooves, which were not seen on the holotype but are present on paratype. Sulcus absent. Prior positions of the anal sinus indicated by recurved ribs on last whorl, and of recurved growth striae on whorl shoulder. Outer lip thin, translucent, without strengthening axial ribs on type specimens. Edge of lip, which is slightly inrolled, forms a flat arc from the anal sinus to anterior canal. Stromboid notch not evident. Anal sinus is a deep notch with a round apex; notch directed laterally, and together with the inner rim flared out appears spout-like. Inner lip narrow, recumbent, emarginated, and thin with an elongate callus that forms the roof of the aperture and parietal side of anal sinus. Anterior canal moderately long, open, turned to the right when viewed ventrally, notched; anterior fasciole not swollen. Color translucent white; varix a pale yellow-brown.

Remarks. Taxonomy. Syntomodrillia floridana possesses the combination of characters that are unique to the genus: a small glossy shell, fusiform, sculpted with ribs extending from suture-to-suture and to the anterior fasciole on the last whorl, a short open aperture, and a varix about ⅓-whorl from the edge of the outer lip. Some specimens of this species may have very weak or possibly lack intercostal grooves. Identification. Syntomodrillia floridana is similar to other small species in the genus, including S. triangulos , new species, S. harasewychi , new species, S. curacaoensis , new species, S. cookie (E.A. Smith, 1888) , and S. woodringi Bartsch, 1934 . From S. triangulos it differs in whorl profile (slightly less convex), in possessing more ribs (12 versus 9–11 on the penultimate whorl), and a protoconch with more whorls (2 versus 1½). From S. harasewychi it differs in the profile of the last whorl (anterior canal curved, not straight) and in possessing weaker intercostal grooves. From S. curacaoensis it differs in whorl profile (less convex) and color (monochromatic, not white with a pale pinkish-brown band). From S. cookei it differs in number of protoconch whorls (2 versus 1¾), in number of ribs on the penultimate whorl (12 not 8–10), and in whorl profile (slightly less convex). From S. woodringi it differs in the number of protoconch whorls (2 versus slightly more than 2), in total length (is smaller, to 7.8 versus 9.7 mm), and in whorl profile (less convex, last whorl less straight).

The two specimens of S. floridana that form the basis for the description of this taxon differ from similar members of the genus-group for characters that have been found to be consistent within species, and so merit description as a separate species. These specimens are interesting because they represent the only described species of Syntomodrillia reported from W Florida.

Etymology. The Florida Syntomodrillia . Named for the state from off which the type specimens have been found.

Figures

PLATE 168. Syntomodrillia floridana, new species. Figs. 1 – 3: holotype, off W Florida, Gulf of Mexico (USNM 900288). 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. Fig. 4: paratype, W of Tampa, Hillsborough Co., W Florida (ANSP 337391).