Decoradrillia festiva, 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 : 117-119

Decoradrillia festiva , new species

(Plate 53)

Type material. Holotype 18.3 x 6.9 mm, F. Ramos!, Jan 2013 (MZSP 122062); 7 paratypes, all from the type locality: 4 spec., 16.6 x 6.6 & 17.2 x 6.5 mm (MNRJ 34635), 18.4 x 6.9 & 19.6 x 7.6 mm (USNM 1291334), in 20 m, off Alcobaça, S Bahia State, F. Ramos!, Jan 2013; 2 spec., 17.0 x 6.6 & 13.4 x 5.1 mm, in 25–27 m, off Alcobaça, S Bahia State, diver L. Meriguetti! (P. Stahlschmidt coll.); 1 spec., 15.2 x 5.8 mm, in 20 m, off Alcobaça, S Bahia State, F. Ramos! Jan 2013 (P. Stahlschmidt coll.).

Type locality. Off Alcobaça, Bahia State, Brazil, in 20– 27 m.

Range and habitat. Known only from the type locality.

Description. Shell small (to 19.6 mm), fusiform, truncated anteriorly, with a tall spire of up to 9¼ whorls, the last about 56% of the shell’s total length, and a short anterior canal. Whorls convex, shoulders strong, round, not angled, sulcus concave; suture appressed, undulant over ribs of preceding whorl. Aperture oval. Protoconch of 2 smooth whorls, diameter of the 1st and 2nd protoconch whorls and 1st teleoconch whorl nearly equal, increasing only slightly, so the shell apex appears acuminate as the whorls expand rapidly after the 2nd teleoconch whorl. Axial sculpture of strong, well defined straight ribs that run from suture-to-suture on spire whorls and to the anterior fasciole on the last, greatly reduced in the sulcus. Ribs narrower than intercostal space, crests narrow, not round, narrowest on ribs of last whorl. Very fine growth striae present, recurved shaped on shoulder reflecting outline of anal sinus. Vari x straight, higher, wider, and with a round crest, not hump-shaped, approximately ¼-turn from edge of the outer lip. Spiral sculpture consists of very fine microscopic grooves, variably spaced, but in mostly sets of 4 with wider spaces between sets, the wider spaces appearing as larger, flattened threads, and all made somewhat wavy by perpendicular growth striae. The pattern may be worn off on part of the shell surface. Although not yet proven to be diagnostic, in an SEM image taken at magnification 1,000x, the narrow spaces on the surface of the holotype’s shell lack rows of punctae, the wider possess 1–2 rows of punctae. Sulcus adjoins suture, is concave, narrow, with low to obsolete ribs. Outer lip thin, flattened from varix to lip edge, usually with a heavy axial fold near lip edge. Lip edge smooth, forming a low to nearly flat arc from anal sinus to stromboid notch, which is shallow but distinct. Anal sinus a deep round notch on shoulder but not adjoining suture, edge of sinus flared upward; opening of sinus partially constricted by parietal callus and outer lip. Inner lip wide anteriorly, erect on anterior portion of canal, recumbent elsewhere, thin on parietal wall, developed into a strong parietal lobe posteriorly; successive layers of deposition show on edges. Anterior canal short, narrow, turned slightly to the right when viewed ventrally; notched. Anterior fasciole with spiral threads, fasciole slightly swollen. Color white or white suffused with pink, with a broad mid-whorl spiral band of brown, dark brown in intercostal space that grades into reddish brown anteriorly; rib shoulders, protoconch, and anterior fasciole white.

Remarks. Taxonomy. Decoradrillia festiva has all of the distinguishing characteristics of the genus: a shell surface microsculpture of microscopic spiral grooves, well-rounded axial ribs that run from suture-to-suture on spire whorls, with only a narrow sulcus, and a high, convex varix that is not hump-like. Variability. The 8 specimens have an average length of 16.96 mm (13.4–19.6 mm) and an average W/ L ratio of 0.383. Identification. Decoradrillia festiva is similar to D. pulchella (Reeve, 1845) and D. colorea , new species. It is somewhat smaller than D. pulchella (16.96 versus 21.71 mm in average total length), has slightly rounder shoulders, and differs in color pattern. It lacks the brown spiral line characteristic of D. pulchella , and has a broader, more intense color band with diffuse boundaries, of dark brown, intense carmine, and rose. The large central band of D. pulchella is usually brown with sharp boundaries, with a faint rose shadow. From D. colorea it differs in possessing fewer ribs with more angular shoulders (7–8 versus 9–10 on penultimate whorl), and narrowed crests, not round, and a different coloration.

Etymology. The Festive Decoradrillia , named for its gaily colored shell. The feminine form ( festiva ) of the Latin adjective festivus, meaning festive.

Figures

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.