Decoradrillia harlequina, 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 : 119-121

Decoradrillia harlequina , new species

( Plates 51 , Figs. 3, 4 & 54)

Crassispira sp.: Humfrey (1975: 182, pl. 22. fig. 7).

“? Unknown”: Williams (2005; 2009: species 9006).

Fenimorea sp. 1: Daccarett & Bossio (2011: 134, fig. 832).

Types. Holotype 16.1 x 6.2 mm (USNM 1291335); 9 paratypes: 4 spec, 17.2 x 6.2 mm (USNM 1291336), 16.9 x 6.3, 14.4 x 6.0 mm (ANSP 464967), and 15.2 x 5.3 mm (MZSP 122063), from the type locality, G. Mackintosh! 4 Aug 1996. 2 spec., 15.0 x 6.0 & 16.4 x 6.2 mm, in 14 m, Annas Shoal, St. Georges, Grenada, G. Mackintosh! 4 Aug 1996 (M. Williams coll.); 3 spec., 15.8 x 6.5, 14.8 x 5.4, & 16.0 x 5.9 (apex gone) mm, in 14 m, Chatham Bay, Union I., G. Mackintosh! 8 Apr 2007 (UF 496635).

Type locality. Devil’s Bay, Grenada, in 14 m.

Other material examined. An additional 12 specimens have been examined: Bahama Is.: 1 spec., 14.5 x 5.8 mm, in 18 m, Indian Cay, Grand Bahama I., 26°42'45''N, 078°39'15''W, J. Worsfold! 16 Apr 1985? (ANSP 366927). St. Martin: 1 spec., 19.5 x 6.8 mm (MNHN, ex J. Colomb coll.). Trinidad & Tobago: 1 spec. 13.8 x 5.3 mm, in 29 m, entrance to Man of War Bay, Tobago I., R. Masino! (author’s coll.); 2 spec., 15.0 x 5.9 & 16.7 x 6.5 mm, in 20 m, Rocky Pt., Mt. Irving Bay, Tobago I., G. Mackintosh! 20 Sep 1998 (M. Williams coll.). Panama: 3 spec., 14.4 x 5.6, 11.6 x 4.3 & 18.1 x 6.2 mm, in 4 m, 5th Cay, Hollandes Cays, G. Mackintosh! 19 Oct 1992 (M. Williams coll.). Belize: 1 spec., 15.2 x 6.6 mm (apex gone), on shallow reef, San Pedro, Ambergris Cay, M. Williams! 8 Oct 1990 (M. Williams coll.).

Range and habitat. Bahama Is. (Grand Bahama I.); Greater Antilles ( Jamaica), Lesser Antilles ( St. Martin; SVG; Grenada); South America ( Trinidad & Tobago: Tobago I.; Colombia: San Andreas Is.); Panama (San Blas Is.: Hollandes Cays); and Belize (Ambergris Cay). Published photographs of specimens from Jamaica (Humfrey, 1975) and Colombia (San Andrea Is.) (Daccarett & Bossio, 2011) are identifiable as this species. This species has been collected in coral reefs in mostly a rather narrow depth range of 10– 29 m. Most specimens exhibit evidence of predator attacks with severe repairs on the spire and body whorls, not counting missing lips, post-varix (which may have been broken in handling). The shell is also very solid, probably a defense against this high predatory pressure.

Description. Shell small, to 19.5 mm, fusiform, truncated anteriorly, up to 11¼ convex, bulging whorls; body whorl an approximately 57% of shell height; aperture moderately wide, columella straight. Protoconch approximately 2½ smooth whorls, well rounded, the first not immersed in the second. Axial sculpture of arcuate ribs on the first teleoconch whorl, which transition into straight ribs by 2nd broad, and the remaining ribs, which are bulging, round-crested and extend from suture-to-suture, broader than intercostal spaces; reduced, narrower, and slightly recurved on shoulder. Ribs number 9–10 on the penultimate, and 7–10 to the varix on the body whorl. Growth striae cover entire shell surface; striae on the trailing sides of ribs run parallel with the ribs; striae on the leading side of the ribs cross over ribs obliquely at rib shoulders; striae in the sulcus are recurved, echoing the shape of the anal sinus. Varix wider and more prominent than the adjacent ribs, located about ¼–⅓-turn back from the edge of the outer lip. Spiral sculpture of 2–3 raised threads on anterior portion of teleoconch whorls, and approximately 17 below the periphery of the body whorl, fairly evenly spaced up to the anterior fasciole. Between the threads are 5 or more finer microscopic threads or grooves, approximately 40/mm on the holotype, which impart a matte finish to shell surface. Sulcus narrow and concave with curved extensions of the ribs and growth striae whose shape reflect the round outline of the anal sinus. Outer lip thin, edge forming a low arc from and congruent with the anal sinus to the stromboid notch. Anal sinus deep and round, constricted by parietal lobe, almost closed in older specimens, edges flared, angled away from shell axis. Inner lip margined, thick at anterior end, thinner on parietal wall, and ending posteriorly in a large tubercle. Anterior canal deep, open, and slightly twisted to the right when viewed ventrally, end of canal flared up dorsally, notched; anterior fasciole slightly swollen; with about 8 spiral threads. Color yellowish white to white base with 3 narrow brown bands, about equal in width, the posterior-most one broken by the crests of the ribs forming a row of brown spots. Only two bands are visible on the spire whorls, one at the suture and the row of spots just above the whorl’s periphery.

Remarks. Taxonomy. Decoradrillia harlequina is an appropriate representative of the new genus because it is widely distributed throughout the Caribbean and possesses strong generic characteristics as the type of the genus should: broad bulging ribs, enlarged, rib-like varix (not hump-like), elongate anterior canal, and presence of closely-packed wavy microscopic spiral threads. Variability. The average total length of 16 unbroken specimens is 15.7 mm (11.6–19.5 mm) and their W/ L ratio is 0.375. The most visible characteristic, its color pattern, is surprisingly constant among specimens examined so far. Those from Tobago I. have a brown, not white anterior fasciole ( Plate 54 , Figs. 11, dorsal view). Identification. Decoradrillia harlequina is not likely to be confused with its congeners on account of its color pattern. It is most similar to Fenimorea petiti Tippett, 1995 but differs in having more swollen ribs, closely packed spiral threads, not the rows of “pits” formed by spiral grooves in F. petiti , and a different coloration.

Etymology. The Harlequin Decoradrillia . The classic harlequin, in a light and dark checkerboard-patterned suit, and this gaily garbed gastropod have a similar comic appeal.

Figures

PLATE 51. Decoradrillia spp. shell surface SEM images. Figs. 1 – 2: Decoradrillia pulchella (Reeve, 1845), Anse Bateau Bay, Tobago I., Trinidad & Tobago (ANSP 338495), 240 x & 930 x, respectively. Figs. 3 – 4: Decoradrillia harlequina, new species: Fig. 3: Indian Cay, Grand Bahama I. (ANSP 366927), 240 x; Fig. 4: holotype, Devil’s Bay, Grenada (USNM 1291335), 1,000 x. Figs. 5 – 6: Decoradrillia interstincta, new species, " Big Rocks ", Utila I., Bay Is., Honduras (ANSP 464986), 250 x & 1,000 x, respectively.

PLATE 54. Decoradrillia harlequina, new species. Upper panel. Figs. 1 – 3: holotype, Devil's Bay, Grenada (USNM 1291335). 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. Lower panel. Fig. 4: paratype, from the type locality (USNM 1291336); Fig. 5: Man of War Bay, Tobago I., Trinidad & Tobago (ANSP 464967); Figs. 6 – 7: paratypes, Annas Shoal, St. Georges, Grenada (P. Williams coll.); Figs. 8 – 9: Hollandes Cays, San Blas Is., Panama (P. Williams coll.); Fig. 10: San Pedro, Ambergris Cay, Belize (P. Williams coll.); Figs. 11 – 12: Mt. Irving Bay, Tobago I., Trinidad & Tobago (P. Williams coll.); Fig. 13: paratype, Union I., St. Vincent & the Grenadines (UF 496635); Fig. 14: St Martin (MNHN, ex J. Colomb coll.).