Splendrillia stegeri (Usticke, 1959) Usticke, 1959

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 : 307-309

Splendrillia stegeri (Usticke, 1959) , new combination

(Plate 158)

Brachycythara stegeri Usticke, 1959 : vi, 83, pl. 4, fig. 14. Nowell-Usticke (1969: 28, pl. 6, fig. 1172); Nowell-Usticke (1971: 25, not pl. 6, fig. 1172); Faber (1988: 89–90, 96 [uncertainty of taxonomic status]); Boyko & Cordeiro (2001: 23 [changed spelling of genus to Brachycithara stegeri ]).

Kurtziella stegeri (Usticke, 1959) : Williams (2005: species 5653 [as nomen nudem]); Rosenberg (2009 [=dubious name]).

Type material. Nowell-Usticke (1959: vi, 83, pl. 4: fig. 14) designates the specimen depicted in fig. 14 as holotype (page vi), which is the specimen in AMNH 195466 according to Boyko & Cordeiro (2001: 23). The specimen measures 4.4 x 1.9 mm. The existence of paratypes is inferred from his given size range (5–6.5 mm). Two other specimens: one in AMNH 195466a, and a 4.5 x 2.1 mm specimen in AMNH 294367, both from Altona Bay, are assumed to be paratypes. The former could not be located during a visit to the AMNH in November 2014 and thus its length not taken. The latter has been damaged by Byrne’s disease and its sculptural detail obscured, although it appeared to be the same species.

Type locality. Altona Bay, St. Croix, U.S. Virgin Is.

Other material examined. Three additional specimens were examined: 1 spec., 4.7 x 2.0 mm, Cabo Rojo, Bahia Salinas, Puerto Rico (P. Williams coll.); 2 spec., 4.7 x 2.0 & 4.5 x 1.9 mm, "The Shacks", Jobos Bay, Puerto Rico (P. Williams coll.).

Range and habitat. U.S. Virgin Is. (St. Croix); Puerto Rico. Also St. Thomas (Water I.) and St. Barts according to Nowell-Usticke (1969; 1971) but not confirmed here. The depth was not stated for type specimens. Other specimens were collected in shallow water.

Description. Shell very small (original description was “average 5.0 mm, maximum 6.5 mm ”, but none of the specimens examined here exceeded 4.7 mm), fusiform, truncated anteriorly; glossy, whorls convex with angular shoulders; spire shorter than body whorl. Holotype in AMNH 195466 of 6 whorls, 4.4 x 1.9 mm overall. Protoconch of 2 round whorls, rapidly expanding from an erect protoconch tip, the second somewhat squat; glossy and opaque white. Axial sculpture of short, regularly spaced, axial ribs. Ribs fade shortly below whorl periphery, and terminate abruptly at shoulder sulcus. Ribs number 13–17 on penultimate whorl, and 12 on body whorl to varix. Varix broad, about ⅓-turn from the edge of the outer lip. Spiral sculpture minimal; spiral ridges faint on shell base but more pronounced on anterior fasciole. Spiral microsculpture of very fine, crowded grooves that cover the shell but are most pronounced in the sulcus. In SEM images the fine crowded spiral grooves on the shell surface appear as crowded rows of closely spaced and contiguous punctae (Pl. 158 Figs. 5–6). Sulcus broad and flat, without axials. Outer lip thin, edge forms a low arch from the sinus to the anterior canal, with only a slight indentation for a stromboid notch. Outer lip joins the suture behind the parietal lobe. Anal sinus wide, anterior side divergent, congruent with the arc of the outer lip, a weak callus present on parietal side. Inner lip thin, unemarginate, a slight lip anteriorly on canal, a weak callus posteriorly in front of the junction of the outer lip. Anterior canal very short, indistinct, open, and straight, unnotched. Color all white, translucent except for opaque ribs, or white with a pair of spiral lines just below whorl periphery such that the posterior-most line shows above the suture line of each whorl. Space between lines and sulcus a dirty white; chestnut patch present on varix.

Remarks. Nomenclature. This species was erroneously placed in Brachycythara , a genus in Mangeliidae , but is instead more properly placed in Drilliidae , having a smooth, glossy, fusiform shell with an approximately 2- whorl protoconch; teleoconch sculpture of axial ribs, with a parietal lobe and anal sinus located adjacent to suture on the whorl shoulder, and a varix behind the outer lip. Taxonomy. Splendrillia stegeri has all the characteristics of Splendrillia : axial ribs that terminate at the sulcus, oblique ribs that fade just below the whorl periphery, and outer lip that joins the suture behind the sulcus. Variability. The average total length of five measured specimens is 4.56 mm (4.4–4.7 mm), and their average W/L is 0.434. Identification. Splendrillia stegeri is unique among its congers for its small size. It most closely resembles S. coccinata (Reeve, 1845) from which it differs in being smaller (4.56 versus 7.88 mm average total length), in possessing ribs that are less oblique, and in possessing more whorl rounded shoulders. It has brown spiral lines not observed in S. coccinata .

Figures

430289); Fig. 1: ventral, lateral & dorsal views; Fig. 2: apical view, V = varix, L = edge of outer lip; Figs. 3 – 4: paratypes (USNM 430038); Fig. 3: ventral and enlarged view protoconch (not to scale) of incompletely developed specimen; Fig. 4: ventral view of decollate specimen. Figs. 5 – 17: ventral views of additional paratypes and specimens from other localities. Figs. 5, 7 – 11: Grand Cul-de-Sac Marin, Guadeloupe. Fig. 5: MNHN IM- 2012 - 28036; Fig. 7: MNHN IM- 2012 - 28047; Fig. 8: MNHN IM- 2012 - 28045; Fig. 9: MNHN IM- 2012 - 28064; Fig. 10: MNHN IM- 2012 - 28045; Fig. 11: MNHN IM- 2012 - 28046; Fig. 6: Anse Tarare, Guadeloupe (MNHN IM- 2013 - 9092); Fig. 12: off Jamestown, Barbados (USNM 900122); Fig. 13: W of Sandy Lane Bay, St. James, Barbados (UF 470278); Figs. 14 – 15: paratypes, off the N coast of Puerto Rico (USNM 429205 a & USNM 429205); Figs. 16 – 18: Minerva seamount, S Bahia, Brazil (P. Stahlschmidt coll.); Fig. 18: apical view of specimen in Fig. 17, V = varix, L = edge of outer lip.