Agladrillia torquata, 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 : 21-23

Agladrillia torquata , new species

( Plate 3 )

Type material. Holotype live-taken, 21.6 x 6.3 mm, 1 Aug 2014 (MNHN IM-2013-56291); 6 paratypes, all juveniles: 1 spec., live-taken, in 300–301 m, 14.2 x 4.5 mm, GUYANE 2014 Sta. CP4366, 07°09′N, 53°05′W, 1 Aug 2014 (MNHN IM-2013-57399); 1 spec., live-taken, 6.1 x 2.7 mm, in 300–301 m, GUYANE 2014 Sta. CP4366, 07°09′N, 53°05′W, 1 Aug 2014 (MNHN IM-2013-56276). Barcode accession numbers for the sequenced holotype and 2 paratypes are tabularized below:

The 4 additional paratypes are: 9.1 x 3.3, 7.8 x 3.0, 5.8 x 2.6 & 3.9 x 1.8 mm in 240 m, Sta. CP4374 GUYANE 2014, 06°40′N, 52°29′W, 3 Aug 2014 (MNHN IM-2000-31086).

Type locality. Off French Guiana, 07°09'N, 53°01'W, in 351–354 m ( GUYANE 2014 Sta. CP4367).

Other material. On the basis of the site’s posted photograph, specimens identified as Agladrillia sp. in the MHNMC on-line database (MOL-1893, MOL-1894, MOL-1895, etc.) are likely this species ( SIAM, 2010). Localities include Bahia Portete, Rio Pedras, and Bocas de Cenza, Colombia, with depths reported at 308– 322 m.

Range and habitat. Colombia; French Guiana. Reported at bathyal depths between 240– 354 m.

Description. Shell small (21.6 mm), glossy, fusiform, to approximately 10 moderately convex teleoconch whorls, their peripheries about mid-whorl, the last 47% of total length, flattened dorso-ventrally and abruptly tapering to a narrow anterior canal. Shell sculpture of knob-like ribs with deep spiral grooves overall. Protoconch eroded in holotype; the paratypes (juveniles) have 1½ glossy-smooth whorls that rapidly expand to a form a globular whorl, the first part of which is slightly out of line with shell axis. Axial sculpture of knob-like ribs at whorl peripheries, just below shoulder sulcus, that curl off like tadpole tails posteriorly onto anterior portion of the sulcus. Knob-like ribs, about as wide as intercostal spaces, are more elongated and opisthocline on the penultimate and last whorls, absent on dorsum of last, and re-appear in sulcus of penultimate and last whorls (weakly so on dorsum) where they are elongate knob-like and prosocline. Ribs number 13 on penultimate and 6 on last whorl to varix. Growth striae distinct, opisthocline, sigmoid on last whorl from anterior fasciole to sulcus, and recurved in sulcus. Spiral sculpture of about evenly spaced deep grooves overall overriding ribs. Grooves strong across the dorsum of the last whorl. Grooves number approximately 6 on penultimate, 12 in shell base, and 10 on anterior fasciole. Sulcus is about ⅓-whorl height, with spiral grooves, and vestigial ribs in the penult and last whorls. Varix hump-like, positioned about ½-turn from edge of outer lip; its position giving the body whorl the appearance of being compressed dorso-ventrally. Outer lip thin, projected out, its edge forming a low almost flat arch from the anal sinus to the stromboid notch, which is broad and deep. The dorsum of the last whorl thin, translucent, and without axial ribs but with some minor folds anterior to the apex of the anal sinus. Anal sinus deep, U-shaped, entrance narrowed by parietal lobe and projecting edge of outer lip. Inner lip margined, erect anteriorly along canal, recumbent and widest on columella, narrowing on parietal wall, and developed into a lobe posteriorly at the anal sinus. Anterior canal moderately long, narrow, flared at its end and with a deep asymmetrical notch. Color white, dorsum of last whorl with an orange-brown patch.

Remarks. Taxonomy. Agladrillia torquata has the distinguishing characteristics of the genus: a varix ½-turn from the edge of the outer lip, a strongly constricted anterior canal, and a lack of ribs on the dorsum of the last whorl. Axial ribs do not run from suture to suture as exhibited by described species, which is not characteristic of other members of the genus. Identification. Agladrillia torquata most resembles Globidrillia smirna (Dall, 1881) which differs principally in lacking strong spiral grooves and a varix about ½-turn from the edge of the outer lip.

Etymology. The Necklaced Agladrillia , from the Latin adjective torquatus, feminine torquata , meaning wearing a necklace. The single row of knob-like ribs at the whorls’ periphery inspired the name.

Figures

PLATE 3. Agladrillia torquata, new species. Figs. 1 – 2: holotype, GUYANE Sta. CP 4367 off French Guiana (MNHN IM- 2013 - 56291). Fig. 1: ventral, lateral & dorsal views; Fig. 2: apical view, V = varix, L = edge of outer lip. Figs. 3 – 7: paratypes (all juveniles) from off French Guiana. Fig. 3: 14.1 mm specimen from GUYANE Sta. CP 4366 (MNHN IM- 2013 - 57399); Figs. 4 – 5: 9.1 mm specimen from GUYANE Sta. CP 4374 (MNHN IM- 201331086, ventral view and enlarged view of protoconch (not to scale), respectively; Fig 6: 6.1 mm specimen from Sta. CP 4366 (MNHN IM- 2013 - 57399); Fig. 7: 3.9 mm specimen from Sta. CP 4374 (MNHN IM- 2013 - 31086). The 5 mm scale bar applies to Figs. 1 – 4; the 2 mm scale to Figs. 6 – 7.