Acteocina interrogens Gofas & Luque, 2021

Gofas, Serge, Luque, Ángel A., Oliver, Joan Daniel, Templado, José & Serrano, Alberto, 2021, The Mollusca of Galicia Bank (NE Atlantic Ocean), European Journal of Taxonomy 785 (1), pp. 1-114 : 73-75

Acteocina interrogens Gofas & Luque sp. nov.

urn:lsid:zoobank.org:act:7B1EE4AD-8C25-4465-B07C-7E65B8F5F5C5

Fig. 30K‒L

Etymology

The specific name refers to shape of the protoconch resembling a question mark.

Type material

Holotype GALICIA BANK • 1 sh ( Fig. 30 K ‒ L , 2.4 mm high); 42°41.94′ N, 11°40.58′ W; 744 m; 31 Jul. 2011; BANGAL 0711 V4; MNCN 15.05 /200141H.

Paratype GALICIA BANK • 1 sh; same collection data as for holotype; MNCN 15.05 /200141P .

Description

Shell small (holotype height 2.4 mm, diameter 1.2 mm), opaque white, cylindrical with a protruding spire. Protoconch of about 1.5 rounded whorls, with a diameter of ca 300 μm, sinistral with a very low spire, its coiling axis forming an angle of ca 100° with coiling axis of teleoconch, markedly protruding and distinctly demarcated from the teleoconch. The holotype has 2.5 teleoconch whorls, slightly convex, only ornamented with faint growth lines; last whorl being about 80% of total height in apertural view, and covering most of the previous teleoconch whorl, adapically with a sharp keel situated at a short distance from the suture and delimiting a flat subsutural shoulder. Aperture occupying two thirds of the total height, broadly rounded abapically and gradually narrowing adapically. Columella curved, continuous with the parietal wall, delimited by a very narrow callus. There is no umbilicus. External lip thin and cutting, straight in its median part, markedly curved at both ends.

Remarks

This species is so distinctive that we describe it despite the very scanty material. Acteocina knockeri (E.A. Smith, 1872) , described from shallow water of Benin, West Africa, is twice as large, with a proportionally tiny hyperstrophic protoconch, and the adapical part of the whorls has two keels and bears axial folds which project, crown-like, on the subsutural flat. Acteocina protracta (Dautzenberg, 1889) , described from deep water off the Azores, also has a much smaller protoconch and the last whorl accounts for 90% of total height in apertural view. We do not know of any Atlantic species approaching this GB species in shell morphology.

Figures

Fig. 30. Heterobranchia 3 (Scaphandridae, Philinidae, Retusidae). A–B. Scaphander punctostriatus (Mighels & C.B. Adams, 1842), BANGAL 0711, V2, 1706 m. 5.8 mm. C. S. punctostriatus, SEM micrograph of the sculpture of the body whorl, BANGAL 0711, V5, 1631 m. D–E. Laona quadrata (Wood, 1839), BANGAL 0711, V5, 4.4 mm. F–G. Pyrunculus ovatus (Jeffreys, 1871), BANGAL 0711, V5, 3.8 mm. H–I. Cylichnium oliviforme (Watson, 1883), BANGAL 0711, V10, 1720 m, 7.6 mm. J. Same specimen, detail of microsculpture of last whorl. K–L. Acteocina interrogens Gofas & Luque sp. nov., holotype (MNCN 15.05/200141H), BANGAL 0711, V4, 744 m, 2.4 mm. Scale bars: A–B, D–I, K–L = 1 mm; C, J = 200 µm.

Fig. 2. Location of benthic samples used in this paper: SEAMOUNT 1 (turquoise), FAUNA II (red), ECOMARG 0709 (green) and INDEMARES BANGAL 0711 (deep blue). Symbols for sampling gears: rock dredge (circles; DW, R or DR), beam trawl (triangles; A, V or CP), otter trawl (squares; G or GOC). Isobaths every 200 m except for shallowest at 700 m; isobaths on the bank proper down to 2000 m from multibeam bathymetry (EEZ Project), completed with GEBCO regional bathymetry for the surroundings.