Akritogyra crenulata Herbert 2024, sp. nov.
Creators: name: Herbert, David G.
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Gastropoda
Seguenziida
Unassigned
Akritogyra
Akritogyra crenulata

description: Akritogyra crenulata sp. nov.
urn:lsid:zoobank.org:act: 8D95E498-B092-4E51-B2D9-86170462B027
Fig. 23
Diagnosis
Shell very small, turbiniform, slightly wider than high, whorls evenly rounded, base umbilicate; subsutural region crenulated by short, broad riblets; intervals between riblets with close-set, microscopic spiral threads; riblets much weaker peripherally; microsculpture comprising numerous close-set microscopic axial threads; riblets reappear on base crenulating umbilical margin; peristome complete, circular, slightly disjunct; interior non-nacreous.
Etymology
From the Latin “ crena, crenatus ” – “a notch, notched”, dim. “ crenula, crenulatus ”; with reference to the subsutural sculpture.
Material examined
Holotype
WALTERS SHOAL • empty shell; slopes, stn DW4886; 33°17′ S, 43°56′ E; depth 573–582 m; 3 May 2017; MNHN-IM-2000-38217.
Paratypes
WALTERS SHOAL • 4 empty shells; same collection data as for holotype; MNHN-IM - 2000-38218.
Description
SHELL. Minute (diameter up to 1.1 mm), turbiniform, slightly wider than high (H/D =0.81–0.93) whorls evenly rounded; periphery at mid-whorl; base umbilicate; teleoconch of up to 2.25 whorls. Early sculpture of short, broad riblets which crenulate subsutural region; intervals between riblets with close-set, microscopic spiral threads (Fig. 23E); riblets weaken considerably in peripheral region, but reappear on base crenulating umbilical margin; peripheral region rendered weakly undulant by remaining traces of axial riblets, but also with numerous close-set microscopic axial threads (Fig. 23F); latter quarter of last adult whorl usually lacking axial riblets below suture; umbilicus of moderate width, its rim rounded and crenulate, its interior with traces of low spiral lirae. Aperture circular, weakly prosocline, peristome complete and a little disjunct from penultimate whorl; outer lip simple; interior smooth, lacking obvious nacre.
PROTOCONCH (Fig. 23G). Globose, moderately exsert, comprising approx. 1.25 whorls, diameter ± 245 μm; with fine superficial granulation where unworn; terminal lip convex, not thickened.
COLOUR. Uniformly translucent milky-white.
DIMENSIONS. Holotype, height 0.85 mm, diameter 1.05 mm; largest specimen, height 1.03 mm, diameter 1.13 mm.
Distribution
Known only from the slopes of Walters Shoal, at a depth of 573–582 m; dredged on coarse sandy substrata; living specimens unknown.
Remarks
I refer this unusual species to Akritogyra simply because it shows some similarity to A. helicella Warén, 1993 from Iceland (Warén 1993). Quite possibly, this similarity is merely superficial, but I know of no other genus to which the species might belong, and choose to place it in Akritogyra rather than create a new genus based on shell characters alone. Akritogyra helicella has similar subsutural crenulation and microscopic, wrinkle-like axial microsculpture, but the shell is much more depressed and the umbilicus is wider. Warén (1993) likewise expressed reservations regarding his referral of A. helicella to Akritogyra, but opted for a conservative approach given the plethora of generic names available for skeneimorph gastropods.
description: Published as part of Herbert, David G., 2024, The Vetigastropoda (Mollusca) of Walters Shoal, with descriptions of two new genera and thirty new species, pp. 1-119 in European Journal of Taxonomy 923 on pages 51-53, DOI: 10.5852/ejt.2024.923.2445, http://zenodo.org/record/10727741