Magnella malmii ( Dall, 1889 )

Figueira, Raquel Medeiros Andrade & Absalão, Ricardo Silva, 2012, Deep-water Raphitomidae (Mollusca, Gastropoda, Conoidea) from the Campos Basin, southeast Brazil, Zootaxa 3527, pp. 1-27 : 13-14

Magnella malmii ( Dall, 1889)

( Figs. 20–21 )

Pleurotomella ( Gymnobela ?) malmii Dall, 1889: 127 : Dall (1881: 70);

Taranis moerchii auct . non Malm, 1861: Dall (1881: 70);

Taranis malmii ( Dall, 1889) : Bouchet & Warén (1980: 78, figs. 167, 272–273);

Gymnobela malmii ( Dall, 1889) : Absalão et al. (2005: 33, fig. 91); Rios (2009: 350, species 909); Pleurotoma pycnoides Dautzenberg & Fischer, 1896: 418 , pl.16, figs. 3, 4: Dautzenberg (1927: 66, pl. 2, figs. 23, 24).

Type material: Not located.

Type locality: Off Havana, Cuba, 1472 m.

Material examined: 18407 [1] OP II # 80; 15980 [3] OP II # 54; 15357 [1] OP I # 74; 17173 [2] OP I # 44.

Description: Shell plump, biconical, white, up to 3.00 mm long. Protoconch with about three whorls. Protoconch 1 with spiral rows of tiny crosses. Protoconch 2 with diagonal cancellation on the lower half of the whorls and axial riblets crossed by very fine and faint spiral threads on the upper half. Clear-cut proto-teleoconch boundary. Teleoconch whorls with one strong subsutural cord and two more spiral cords on the lower half of the whorls, crossed by 13–15 strong axial ribs (on the second whorl). Nodules on the intersections of the ribs with the two lower spiral cords, but the subsutural cord shows large nodules which are not strictly related to the axial sculpture. Slightly depressed area separates the subsutural cord from the lower half of the whorls, and the axial ribs are fainter in this part. Shell surface covered by spirally aligned granules. Suture well marked. Base short, axial ribs vanishing toward the aperture and about 10 spiral cords. Anal sinus not discernible. Inner lip reflected over parietal wall. Outer lip thick. Anterior siphonal canal oblique, short and wide. Aperture elliptical.

Geographic distribution: Northeast Atlantic: Azores ( Dautzenberg & Fischer, 1896; Dautzenberg, 1927; Bouchet & Warén, 1980). Northwest Atlantic: Cuba ( Dall, 1889); Florida ( Bouchet & Warén, 1980). Southwest Atlantic: Espírito Santo and Rio de Janeiro ( Absalão et al., 2005); Campos Basin, Rio de Janeiro (this paper). Bathymetry: 225 m ( Bouchet & Warén, 1980)– 1472 m ( Dall, 1889).

Discussion: This species was described by Dall as a variation of Pleurotomella ( Gymnobela ?) tornata Verrill, 1884 , which itself was described as a variation of Taranis moerchii Malm, 1861 . When describing the species Dall was unsure of the generic placement, but he stated that it should be in the vicinity of Pleurotomella and Gymnobela , mostly on account of the diagonally cancelled protoconch. Tucker (2004) considered the three forms as synonyms, whereas Bouchet & Waren (1980: 74) distinguished Taranis malmii from T. moerchii . We agree with Bouchet & Waren (1980) that the species are not synonyms, but we believe the best generic placement for malmii is in the genus Magnella as previously suggested by Kilburn (1991: 326) and proposed by Figueira & Absalão (2010b: 737). Although M. malmii was described as a variation of P. tornata and the latter is a variation of T. moerchii , M. malmii is very different from both. In fact, P. tornata is a synonym of T. moerchii and M. malmii can be distinguished from them by the presence of a strong subsutural cord (which is a diagnostic character of the genus Magnella ), a tall teleoconch without a marked shoulder and a diagonally cancelled protoconch.

We could not locate the type material of this species. The holotype mentioned by Bouchet & Warén (1980: 80) with the collection number USNM 87433 does not match the locality mentioned in Dall’s original description (1889: 127). According to Dall, the holotype was collected in station #2 at 1472 m, whereas the specimen USNM 87433 is from station # 43, 620 m.

Figures

FIGURES 20 – 26. 20, 21 — Magnella malmii (Dall, 1889), IBUFRJ 15980; 20 — 3,00 mm, whole shell; 21 — protoconch. Figures 22, 23 — Magnella watsoni (Dautzenberg, 1889), IBUFRJ 14967; 22 — 4.94 mm, whole shell; 23 — protoconch. Figures 24, 25, 26 — Magnella extensa (Dall, 1881); 24 — IBUFRJ 18474, 3.30 mm, whole shell; 25 — IBUFRJ 18474, protoconch; 26 — Syntype MCZ 7147. Scale bars: 20 and 24 = 500 μm; 21, 23 and 25 = 250 μm; 22 and 26 = 1 mm.