Agladrillia aureola, 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 : 18

Agladrillia aureola , new species

( Plate 1 )

Agladrillia (?) lassula auct. non Jung, 1969 is a misidentification by Petuch (1981: 311, 338; figs. 109, 110) for living specimens from Venezuela (Falcon: Gulf of Triste, not examined). A. lassula was described from the Springvale Formation of Trinidad (Jung, 1969: 550, pl. 59, figs. 1–3) [=Late Pliocene (Carr-Brown & Frampton, 1979)].

Agladrillia lassula auct. non Jung, 1969 are misidentifications by Williams (2009: 1501, [right photo only]) and Daccarett & Bossio (2011: 128–129, fig. 777) that are likely this species.

Type material. Holotype 12.0 x 4.3 mm, G. Mackintosh! 9 Nov 1999 (USNM 1291318); 2 paratypes: 1 spec., 11.1 x 4.3 mm, in 9 m, S side of Coche I., Venezuela, G. Mackintosh! 3 Sep 1999 (ANSP 464965); 1 spec., 10.3 x 3.9 mm, in 15–18 m, Caribe & Lobos Is., near Coche I., Venezuela, G. Mackintosh! Sep 1999 (P. Stahlschmidt coll.).

Type locality. Bahia Guamache I., Margarita I., Venezuela, in 5 m on hard-packed sand.

Range and habitat. Venezuela (Margarita I.; Coche I.), at depths between 5.5–18.0 m. If the specimen depicted in Daccarett & Bossio is this species, then the range would include Colombia (Magdalena Dept.) to the north.

Description. Shell small (to 12.0 mm in total length), glossy, fusiform, to approximately 10 moderately convex whorls, their peripheries approximately mid-whorl, the last about 55% of total length, flattened dorsoventrally and rapidly tapering to a narrow anterior canal. Shell sculpture of ribs with deep intercostal spiral grooves. Protoconch of approximately 1½–1¾ smooth translucent whorls, becoming sub-carinate on last ½–¾ whorl, the first not immersed in the second. Axial sculpture narrow ribs that run from suture-to-suture on spire whorls evanesce at anterior fasciole of last whorl, absent on dorsum of last except in sulcus; intercostal spaces greater than their width. Ribs straight, then crescent shaped in sulcus, number 9–10 on penultimate and 5–8 on last whorl to varix. Spiral sculpture of evenly spaced deep grooves in intercostal spaces (rib crests are smooth) more closely spaced in sulcus. Grooves present across the dorsum of the last whorl. Grooves give the appearance of closely packed spiral cords, number approximately 7 on penultimate, 10 in shell base, and 7 on anterior fasciole. Sulcus is marked by crescent-shaped ribs on the whorl shoulder that are lower than the sigmoid ribs on the whorl face, ribs overridden by spiral grooves giving sulcus the appearance of having 3–4 spiral cords. Varix hump-like, positioned ½-turn from edge of outer lip; its position resulting in the appearance of the body whorl of being compressed dorso-ventrally. Outer lip thin, projecting, its edge congruent with and from anal sinus forming a low almost flat arch to stromboid notch where it is bent out at the stromboid notch and follows the anterior canal; stromboid notch deep. The dorsum of the last whorl is thin, translucent, and except for their presence in the sulcus, ribs obsolete; to 4 minor axial folds present on the last ¼ turn. Anal sinus deep, U-shaped, entrance slightly constricted by parietal lobe, inner edge flared out. Inner lip erect anteriorly along canal, recumbent and widest on parietal wall and developed into a lobe posteriorly at the anal sinus. Incremental growth layers visible on side of parietal lobe. Anterior canal moderately long, narrow, open and turned slightly to the right and dorsally; deeply notched. Color golden yellow, rib crests lighter, varix white and dorsum of last whorl orange brown.

Remarks. Taxonomy. Agladrillia aureola has the characteristics of Agladrillia : a varical hump ½-turn from the edge of the outer lip, strongly constricted anterior canal, and a dorsum on last whorl mostly devoid of ribs. Variability. The average length of three specimens is 11.13 mm (11.1–12.0 mm) and average W/ L ratio is 0.375. Identification. Agladrillia aureola most closely resembles A. rhodochroa (Dautzenberg, 1900) . It differs in color, which is golden yellow with an orange brown varical spot, not pink with a brown varical spot, and in relative whorl height, which is shorter in A. rhodochroa . Also, whorls are more convex and axial ribs less oblique than in A. rhodochroa . From Calliclava tobagoensis , new species A. aureola differs in possessing a smooth protoconch, a greater constriction of the anterior canal and a varix located ½-turn from the edge of the outer lip. The latter species has a carinate protoconch, a less-constricted anterior canal, and a varix located about ⅓-turn from the edge of the outer lip.

Etymology. The Gold colored Agladrillia , from the Latin adjective aureolus, feminine aureola , meaning golden or gold colored. The color seems to consistently differentiate this species from the somewhat similar A. rhodochroa , which has some violet, pink or rose color.

Figures

PLATE 1. Agladrillia aureola, new species. Upper panel. Figs. 1 – 3: holotype, Bahia Guamache I., Margarita I., Venezuela (USNM 1291318). Fig. 1: ventral, lateral & dorsal views; Fig. 2: apical view, V = varix, L = edge of outer lip; Fig. 3: enlarged view of protoconch (not to scale). Lower panel. Figs. 4 – 5: paratypes. Fig. 4: S side of Coche I., Venezuela (ANSP 464965); Fig. 5: Caribe & Lobos Is., near Coche I., Venezuela (P. Stahlschmidt coll.).