Alvania selsoifensis Bouchard, Wesselingh, Pouwer & Landau, 2025, n. sp.
Creators: name: Bouchard, Blanche
name: Wesselingh, Frank P.
name: Pouwer, Ronald
name: Landau, Bernard
Publisher: name: Zenodo
Year: 2025
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Gastropoda
Littorinimorpha
Rissoidae
Alvania
Alvania selsoifensis

description: Alvania selsoifensis n. sp.
(Fig. 8B 1-B 3)
urn:lsid:zoobank.org:act: 19AACEFD-F1BE-4FF6-B380-411C58ACC056
TYPE MATERIAL. — Holotype: RGM.1365286, height 1.4 mm, width 0.9 mm, leg. ACJ.
ETYMOLOGY. — Named after the type locality of Selsoif.
TYPE LOCALITY. — Selsoif, Saint-Sauveur-le-Vicomte, Manche department, NW France.
STRATUM TYPICUS. — Gelasian, Early Pleistocene.
DIAGNOSIS. — Alvania species of the A. dictyophora -complex with biangular whorls, deeply impressed suture, two elevated primary cords on spire whorls, three above the insertion of the outer lip on the last whorl, three further strong cords over base, axial sculpture 12-13 sharp ribs that weaken over base, base somewhat depressed.
DISTRIBUTION. — Lower Pleistocene: Atlantic, endemic to Selsoif, NW France (this paper).
DESCRIPTION
Shell small, rissoiform. Protoconch of two smooth whorls (surface sculpture may be abraded). Three teleoconch whorls; sculpture on spire whorls of two elevated spiral cords; axial sculpture of 12-13 narrow, elevated, widely spaced, orthocline ribs forming coarsely reticulated pattern. Whorl profile sharply angled at the cords. Last whorl 60% of total height, single secondary develops on second half of last whorl, profile sharply angular at shoulder and peripheral cord, peribasal cord prominent with two further cords of equal strength over base, axials weakening over base: base somewhat depressed. Aperture 35% of total height, ovate; outer lip thickened by varix, peristome complete; columella thickened in abapical portion.
REMARKS
Alvania selsoifensis n. sp. is a very distinctive Alvania species and merits formal description. Unfortunately, all other specimens are too incomplete to nominate as paratype material. Alvania selsoifensis n. sp. might belong to the A. dictyophora -complex of Amati & Smriglio (2016) characterised by having relatively coarsely reticulated surface sculpture with two cords on the spire whorls, although all the species included in the complex by those authors are endemic to the Pliocene to present-day of Italy. The Selsoif species differs from A. dictyophora (Philippi, 1844) and A. desabatae Amati & Smriglio, 2016 in having a deeper suture making the whorls more angular, and only three cords above the insertion of the outer lip on the last whorl as opposed to four in A. dictyophora. It is more closely similar to A. clathrella (Seguenza, 1903), a Pleistocene to extant species from Italy, in having two primary cords on spire whorls and widely spaced axials forming a reticulated pattern. However, the Selsoif species differs in having a deeper suture, fewer axials on the spire whorls resulting in a slightly denser reticulated pattern and the cords over the base are thinner and the reticulation stronger, whereas in the Selsoif species the cords over the base are stronger and broader and the axials weaker giving the base a strongly corded rather than reticulated appearance. Alvania bicingulata (G. Seguenza, 1876) from the Pliocene of Sicily differs in having a more superficial suture, a more rounded last whorl, and, like A. clathrella has reticulated sculpture on the base. The last species included in the group by Amati & Smriglio (2016), A. tenuicostata (G. Seguenza, 1876), another fossil species from the Pliocene of Sicily is far more elongate with weaker sculpture. If we review species with similar shell characters outside the Mediterranean, A. milleti Landau, Ceulemans & Van Dingenen, 2018 from the Atlantic Tortonian Upper Miocene of NW France could also be included, but like A. clathrella this species has a more superficial suture, and the base is less depressed and reticulated.
description: Published as part of Bouchard, Blanche, Wesselingh, Frank P., Pouwer, Ronald & Landau, Bernard, 2025, The Gelasian gastropod fauna of Selsoif (Manche, France), pp. 39-91 in Geodiversitas 47 (3) on page 59, DOI: 10.5252/geodiversitas2025v47a3, http://zenodo.org/record/14823602