Splendrillia compta, 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 : 292-293

Splendrillia compta , new species

( Plate 148 )

Type material. Holotype 12.4 x 4.8 mm, A. Bodart! March 1999 (MZSP 122075); 3 paratypes: 10.2 x 4.3, 11.0 x 4.5 & 13.0 x 5.2 mm, in 20–30 m, off Rio do Fogo, Rio Grande do Norte, Brazil, local people! Apr–Sep 2008 (P. Stahlschmidt coll.).

Type locality. off N Natal, Rio Grande do Norte, Brazil, in 10– 20 m.

Range and habitat. Brazil (Rio Grande do Norte State). Reported from 10– 30 m.

Description. Shell small (to 13.0 mm in total length), fusiform, truncated anteriorly, glossy, with up to 8¾ convex whorls, suture appressed, last whorl approximately 59% of shell length; aperture narrowly oval; anterior canal very short. Protoconch paucispiral, of 1¾–2 smooth, round whorls, first not immersed in second. Axial sculpture of strong rather narrow slightly opisthocline ribs with convex, shouldered ribs that run from suture-tosuture, are much reduced and arcuate in a narrow band below suture but less so on later whorls, then evanesce at anterior fasciole on body whorl; spaces between ribs about as wide as the ribs, 10–11 on the penultimate, 6–7 on body whorl to the varix. Strong growth striae are present that run obliquely over the ribs and are recurved on the whorl’s shoulder. Varix is like an enlarged rib, higher and about twice the width of adjoining ribs, but straight, not opisthocline. Spiral sculpture consists of about 6 spiral ridges on anterior fasciole. As seen under a dissecting microscope, very faint microscopic lines cover the shell surface. These resolve into rows of punctae in SEM images (see Pl. 141, Figs. 5–6). Sulcus indistinct, indicated only by the reduced, arcuate ribs and striae on the shoulder that mark the prior positions of the anal sinus. Outer lip flattened from varix to lip’s edge, inrolled at edge from above stromboid notch to anal sinus, and strengthened by an axial fold near the edge of the lip; edge forms a very low arc, almost straight, from the anal sinus to the stromboid notch. Stromboid notch very weak. Anal sinus a deep notch with a rounded apex that adjoins the suture behind the parietal callus. Inner lip thick, detached anteriorly, thin on the parietal wall forming a parietal lobe posteriorly. Anterior canal very short, open, deeply notched, edge upturned dorsally. Anterior fasciole moderately swollen, with about 6 spiral ridges. Color creamy white with 4 light golden brown bands, the widest mid-whorl, and all partially interrupted by white rib crests; aperture white. Bands are pale brown to reddish brown on paratypes.

Remarks. Taxonomy. Splendrillia compta has most of the characteristics of the genus Splendrillia in possessing a glossy shell without spiral sculpture, a very short anterior canal with no post stromboid notch inflection of the outer lip, and anal sinus that hooks up to the suture behind the parietal lobe. It diverges from most members of the genus in that it lacks a completely bare sulcus as ribs are present, though much reduced, possessing a varix that is narrow, not hump-like, and in having ribs that extend to the anterior fasciole. The ribs terminate just below the whorl periphery on the base of most members of the genus. The characteristics of S. compta are more closely allied to Splendrillia than any other genus but the differences suggest the possibility of an as yet unnamed subgroup within the genus. Variability. The four specimens have an average total length of 11.65 mm (10.2–13.0 mm) and an average W/ L ratio of 0.404. The color of the spiral bands varies among individuals. Identification. Splendrillia compta is closest to S. masinoi , new species, and it is somewhat similar in color pattern and size to S. karukeraensis , new species, S. cruzensis , new species. From S. masinoi it differs in having longer, more convex but less angular ribs and a narrower varix. The shell appears stockier and color patterning is also different. From S. karukeraensis and S. cruzensis it differs in possessing higher, more convex ribs that are only slightly opisthocline, not low and noticeably opisthocline as in the latter two species. These latter two also have a wider, smoother sulcus, and different coloration.

Etymology. The Ornate Splendrillia . From the Latin adjective comptus, meaning adorned or ornate, feminine compta , a reference to the pretty effect of spiral bands of color, which vary among specimens, on well-formed glossy ribs.

Figures

PLATE 148. Splendrillia compta, new species. Figs. 1 – 3: holotype off N Natal, Rio Grande do Norte, Brazil (MZSP 122075). 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 – 6: paratypes from off Rio do Fogo, Rio Grande do Norte, Brazil (P. Stahlschmidt coll.).