Mikro oviceps Ortega & Gofas 2019, n. sp.
Creators: name: Ortega, José Rafael
name: Gofas, Serge
Publisher: name: Zenodo
Year: 2019
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Gastropoda
Trochida
Skeneidae
Mikro
Mikro oviceps

description: Mikro oviceps n. sp.(Fig. 4 A-H)
urn:lsid:zoobank.org:act: D9DA7056-2000-417A-92C5-AEE1AF757354
TYPE MATERIAL. — Holotype. sh., MNHN-IM- 2000-34255. Paratypes. 24 sh., MNHN-IM-2000-34256, all from SEAMOUNT 2, DW 130.
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 meaning “egghead”, referring to the shape of the protoconch.
DESCRIPTION
Shell minute, globular in shape, with a moderately high, somewhat cyrtoconoid spire and a distinct umbilicus. Protoconch proportionally very large, egg shaped with no sign of coiling, with a maximum diameter of 270 µm, separated from the teleoconch by a distinct scar; protoconch surface with a microscopically pitted texture seen only at high magnification under the SEM. Teleoconch of about 1 3/4 whorl. Spire whorls with a weak spiral cordlet running along the suture, a very distinct adapical shoulder delimited by a sharp keel, channelled between the suture and the keel and slightly convex below it. Surface mostly smooth except for growth lines, a cluster of 4-6 spiral cordlets below the periphery of the last whorl, and another cluster of three stronger spiral cords surrounding the umbilicus. Aperture with a somewhat rhomboidal shape, with the adapical part definitely angled. Outer lip rather thick but simple, orthocline; parietal area without any callosity, columellar edge of the aperture increasing in thickness abapically. Umbilicus open, deep and relatively broad, inside with axial growth lines of a very rough texture, and with an additional spiral cord situated deep inside and abutting into the abapical part of the columella.
Colour opaque white, with a somewhat pearly aspect, the protoconch slightly yellowish. Maximum diameter up to 0.8 mm (holotype 0.84 mm height × 0.80 mm diameter).
REMARKS
The generic assignment of this species is tentative; shared characters with the type species Mikro globulus Warén, 1996 are the minute size, the protoconch with a rough but not distinctly sculptured surface, the presence of a distinct adapical keel at a short distance from the suture, and of a distinct spiral ridge inside the umbilicus. Lopheliella Hoffmann, van Heugten & Lavaleye, 2008 is similar in shape but has a distinct honeycomb sculpture on the protoconch which is not seen here; Lopheliella also either lacks an internal ridge inside the umbilicus or has it very close to its edge, not far inside as in Mikro globulus. Lopheliella species are also considerably larger, with an adult size of 2 to 3 mm.
Mikro oviceps n. sp. is unique in having a protoconch which shows no sign of coiling, contrary to M. globulus and M. hattonensis Hoffman, van Heugten & Lavaleye, 2010 which were also collected in the same dredge haul.
Mikro globulus (Fig. 4 I-L) is similar in size but has a higher spire, not cyrtoconoid. It lacks the clusters of spirals on the periphery and the abapical part of the last whorl; the subsutural shoulder disappears on the later whorls, and the umbilicus is narrower with only one periumbilical ridge, and no spirals inside. Mikro hattonensis (Fig. 4 M-P) is more similar to M. oviceps n. sp. in outline, but also lacks the spirals on the last whorl and is more broadly umbilicate. Both M. globulus and M. hattonensis have a protoconch as usual in Vetigastropoda i.e. coiled with hardly more than half a whorl (Fig. 4L, P). Both also have been found in the same sample as M. oviceps n. sp. and are new records for Spanish waters (see below).
description: Published as part of Ortega, José Rafael & Gofas, Serge, 2019, The unknown bathyal of the Canaries: new species and new records of deep-sea Mollusca, pp. 513-551 in Zoosystema 41 (26) on page 520, DOI: 10.5252/zoosystema2019v41a26, http://zenodo.org/record/3726028