( 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).