Orbitestella pruinosa, Ortega & Gofas, 2019

Ortega, José Rafael & Gofas, Serge, 2019, The unknown bathyal of the Canaries: new species and new records of deep-sea Mollusca, Zoosystema 41 (26), pp. 513-551 : 542

Orbitestella pruinosa n. sp.

( Fig. 25 D-F)

urn:lsid:zoobank.org:act:340AD666-39F8-4250-842D-443F7546E7E0

TYPE MATERIAL. — Holotype. sh., MNHN-IM-2000-34277, from SEAMOUNT 2 DW130 .

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

ETYMOLOGY. — Latin adjective meaning “frosty”, alluding to the texture given to the shell surface by the miscrosculpture.

DESCRIPTION

Shell minute, depressed, with a flat spire and wide umbilicus. Protoconch of a little less than 1 whorl. Teleoconch with three strong spiral ridges, of which one is adapical, the strongest one is on the periphery, and one is abapical. Microsculpture of irregularly arranged granules, loosely aligned axially, which give the surface a shagreened aspect and are attenuated on the ridges; the last 1/4 whorl marked in addition by conspicuous growth lines. Umbilicus broad and wide, delimited by an additional internal ridge. Aperture simple, rounded on the parietal and columellar side, polygonal along the outer lip, reflecting the termination of the ridges. Columellar edge of the aperture reflected outwards and strongly receding where approaching the parietal edge, abutting there on the abapical ridge of the preceding whorl. Dimensions of the holotype: 0.35 mm height × 0.8 mm diameter.

REMARKS

The size, profile, and the characteristic recession of the abapical part of the aperture support the placement of this species in Orbitestella . The protoconch is damaged on the only available specimen and could not be observed properly.

This minute species does not resemble closely any other gastropod known to us from the eastern Atlantic. The most similar is Orbitestella hinemoa Mestayer, 1919 , from off New Zealand, which differs only in having a more even development of the three keels on the last whorl, the peripheral one not so much protruding as in Orbitestella pruinosa n. sp. The only other species of Orbitestella described from the eastern Atlantic and Mediterranean area is O. dariae (Liuzzi & Zucchi Stolfa, 1979) , recorded from Madeira by Segers et al. (2009). It has a similar outline but an evenly convex abapical part with several flat spiral cords, and a spiral series of prominent knobs on the adapical side; furthermore it lacks the shagreened microsculpture of O. pruinosa n. sp. The specimen from a deep-water thanatocenosis off Sardinia, Western Mediterranean, figured as O. dariae by Bonfitto et al. (1994) is not that species and is so similar to O. pruinosa n. sp. that it is possibly the same; their specimen differs from the Canarian one in having definite axial riblets between the spiral ridges, instead of loosely aligned granules.

Figures

FIG. 25. — A-C, Spirolaxis lamellifer (Rehder, 1935), shell from DW120 (diameter 3.7 mm); new to the Canaries; D-F, Orbitestella pruinosa n. sp., holotype from DW130 (diameter 0.8 mm); G, Graphis gracilis (Monterosato, 1874), shell from DW130 (height 2.1 mm); H, I, Odostomia madeirensis Peñas, Rolán & Swinnen, 2014, shell from DW133 (height 2.2 mm); new to Spanish waters; J, K, Liostomia canaliculata n. sp., holotype from DW130 (height 1 mm); L, M, Ringicula pirulina Locard, 1897, shell from DW130 (6.4 mm); N, Colpodaspis pusilla M. Sars, 1870, shell from DW126 (1.4 mm); new to the Canaries.