Dentimargo crassidens Ortega & Gofas 2019, n. sp.

Dentimargo crassidens n. sp.

(Fig. 17 A-E)

urn:lsid:zoobank.org:act: 30097341-98F6-40FC-A68B-69B7BCB348C1

TYPE MATERIAL. — Holotype. sh., MNHN-IM-2000-34265. Paratypes. 3 adult sh. and 1 immature spm., MNHN-IM-2000-34266, SEAMOUNT 2 DW130.

TYPE LOCALITY. — Off NW Gran Canaria, 28°08.95’N, 15°53.11’W / 28°09.06’N, 15°52.92’W, 655- 660 m.

ETYMOLOGY. — From the Latin adjective crassus, thick, and dens, a tooth, alluding to the thick labial denticle.

OTHER MATERIAL EXAMINED. — 1 sh., DW128. — 47 sh. (12 immature and 35 in early postlarval stage), DW130.

DESCRIPTION

Shell small, dirty white, very solid, smooth, consisting of 4 1/2 whorls with an elevated but blunt spire; protoconch 1.4 mm in diameter, consisting of about 1 3/4 whorl, slightly brownish in colour, delimited from teleoconch by a tenuous but definite line. Spire whorls very slightly convex, with a thin but distinct suture. Last whorl representing about 80% of total height. Aperture elongate, narrow, parallel-sided except for a very prominent and broad denticle situated on the inner side of the outer lip, at its upper 1/4 adapically. Outer lip bordered externally by a broad thickened labial varix, slightly receding at its adapical end, forming there a distinct shoulder against the penultimate whorl. There are four columellar plaits, stout with a flattened crest, decreasing in size towards the abapical part of the columella. No columellar callus. Dimensions of holotype: 10.0 mm height × 4.7 mm diameter.

REMARKS

There are four North-East Atlantic species currently assigned to the genus Dentimargo, diagnosed by having a strong denticle on the adapical part of the outer lip: D. hesperia (Sykes, 1905), D. bojadorensis (Thiele, 1925), D. auratus Espinosa, Ortea & Moro, 2014 and D. giovannii Pérez-Dionis, Espinosa & Ortea, 2014, the latter with a type locality in the Canary Islands (Espinosa et al. 2014). The first was described from deep water off SW Spain and is the most similar, but it is smaller (7-8 mm), stouter, with a distinctly broader aperture, columellar plaits with a more acute crest, and the outer lip is not so thickened. The figure in Sykes (1905) shows a more pointed anterior end and a still less prominent labial denticle than the syntype pictured in Bouchet & Warén (1985), but in any case Sykes described the aperture as “broad”.

Dentimargo bojadorensis was described from a depth of 146 m off the mainland African coast. It is smaller, more fusiform without a distinct shoulder at the insertion of the outer lip, which narrows considerably at its adapical termination. The inner labial denticle is also different, situated towards the upper 1/3 of the aperture and more elongate, plait-like.

Dentimargo giovannii, described from the bathyal level (607 m) near Isla de Lobos between Fuerteventura and Lanzarote, and D. auratus, described from shallow water (20 m) off Cape Blanco, Mauritania, are both distinguished by their extremely high spire, with the insertion of the outer lip situated about mid-height of the shell (near the upper third in Dentimargo crassidens n. sp.) and also by the characteristically pointed shape of the abapical end (see Espinosa et al. 2014).