Alvania sleursi
Creators: name: Sacchetti, Claudia
name: Landau, Bernard
name: Ávila, Sérgio P.
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Gastropoda
Littorinimorpha
Rissoidae
Alvania
Alvania sleursi

description: Alvania sleursi (Amati, 1987)
Plate 3 B, C 1 -C 2
* Manzonia (Alvinia) sleursi Amati 1987: 26, figs. 1-2.
Alvania sleursi (Amati, 1987) — Ávila et al. 2002: 353, figs. 54-56, 58-61.
Alvania sleursi (Amati, 1987) — Martins et al. 2009: 62, pl. 9, figs. 141-142.
Alvania sleursi (Amati, 1987) — Ávila et al. 2009b: 20, 23, 26.
Alvania sleursi (Amati, 1987) — Ávila et al. 2010: 36, fig. 28 (1-6).
Alvania sleursi (Amati, 1987) —Ávila 2013: 110, fig. 5B.
Alvania sleursi (Amati, 1987) — Meireles et al. 2013: 141, fig. 5G.
Alvania sleursi (Amati, 1987) — Ávila et al. 2015a: 137, 139, 142.
Alvania sleursi (Amati, 1987) — Amati & Chiarelli 2017: 841, fig. 17.
Santa Maria material examined. Maximum height 3.2 mm, width 1.8 mm. DBUA-F 962-3 (1), DBUA-F 1058- A (1), DBUA-F 827-B (3), DBUA-F 471-4 (1), Ponta do Castelo; DBUA-F 1044- A (1), Pedra-que-pica, Santa Maria, Azores, Touril Complex, Lower Pliocene.
Description. Shell medium sized for genus, rissoiform, imperforate, with scalate spire. Protoconch paucispiral, of 1.5 whorls, nucleus medium sized, post-nuclear whorl bearing spiral cords.Teleoconch of three shouldered whorls, subsutural ramp moderately wide, delimited by adapical spiral cord, weakly convex below. Suture undulating and weakly impressed. Sculpture of axial ribs and spiral cords, about one-third as wide as their interspaces, forming a square reticulate pattern. Axial sculpture of strong, orthocline, rounded ribs, about 14 on penultimate whorl. Spiral sculpture of strong rounded cords, two on spire whorls, with a third appearing just above the abapical suture on second half of penultimate whorl with pointed tubercles developed at sculptural intersection. Last whorl 70% of total height, with three spirals placed above aperture, two further spirals over base. Aperture ovate, peristome complete. Outer lip greatly thickened by broad labial varix bearing coarse tubercles where the spiral cords run onto the lip, inner edge bevelled, smooth within, anal sinus shallow. Peristome broad and greatly thickened.
Discussion. Alvania sleursi (Amati, 1987) is characterised by its paucispiral protoconch bearing spiral cords, scalate spire whorls, and coarsely cancellate teleoconch sculpture with two spiral cords on spire whorls and three above the aperture on the last whorl. The Pliocene specimens from the Azores are some of the few in which the protoconch is preserved and confirms the identification. Today, A. sleursi is reported from the Azores, Madeira and Selvagens (Hoenselaar & Goud 1998: Ávila 2000b; Freitas et al. 2019). It seems therefore, that these two species of Alvania species (A. mediolittoralis and A. sleursi) was already present in the Lower Pliocene. For further discussion see under A. cancellata (da Costa, 1778).
Distribution. Lower Pliocene:Atlantic, Santa Maria Island, Azores (Meireles et al. 2013). Present-day, Atlantic, Azores (Amati 1987; Hoenselaar & Goud 1998; Ávila 2000; Martins et al. 2009; Ávila et al. 2009b; Amati & Chiarelli 2017), Madeira and Selvagens Archipelago (Hoenselaar & Goud 1998).
Genus Rissoina d’Orbigny, 1840
Type species. Rissoina inca d’Orbigny, 1840 (d’Orbigny 1840: 394), by monotypy. Present-day, Peru.
description: Published as part of Sacchetti, Claudia, Landau, Bernard & Ávila, Sérgio P., 2023, The Lower Pliocene marine gastropods of Santa Maria Island, Azores: Taxonomy and palaeobiogeographic implications, pp. 1-150 in Zootaxa 5295 (1) on pages 48-49, DOI: 10.11646/zootaxa.5295.1.1, http://zenodo.org/record/7965273