Class Gastropoda Cuvier, 1795
Family Rissoidae Gray, 1847
Genus Alvania Risso, 1826
Species Alvania discors (Allan, 1818)
Alvania discors (Allan, 1818)
Not common in the Tuscan Pliocene, best known from lower Pleistocene.
Gastropoda Rissoidae Alvania Alvania discors Pliocene
Description
(O.D.) Shell pointed, with strong longitudinal ribs and transverse striae; inside ribbed; body whorl, about equal to the length of the spire. Length 1½ eighth of the inch.
Conchiglia piccola, conica, robusta, formata da 6-7 giri poco convessi e separati da suture profonde. Protoconca di circa due giri ornata da file di papille irregolari variamente disposte. I giri della teleoconca sono ornati da 11-12 coste assiali robuste, rette e separate da intervalli più ampi. Cingoli spirali quattro, forti e alti, separati solchi più stretti. Ultimo giro arrotondato alla periferia con base convessa percorsa da cinque cingoli concentrici, separati da intervalli più stretti. Apertura piriforme con labbro esterno robusto internamente denticolato e bordo columellare liscio con callo poco esteso (Chirli).
Shell small, conical, robust, formed by 6-7 little convex whorls, separated by deep suture lines. Protoconch of about two whorls with rows of irregularly arranged papillae. Axial ornamentation of teleoconch consisting of 11-12 robust ribs, straight and separated by wider intervals. Spiral threads four, strong and high, separated by narrow grooves. Last whorl rounded to the periphery, with convex base crossed by five concentric threads, separated by narrower intervals. Pyriform aperture with a sturdy external lip, internally denticulated. Smooth columellar edge with a little extended callus.
Bibliographic references and some more common synonyms
1818 Turbo discors – Allan, p. 463, pl. 10, fig. 5
1818 Turbo discrepans – Allan, p. 463, pl. 10, fig. 4
1826 Rissoa de Montagu – Payraudeau, p. 111, pl 5, fig. 14
1826 Alvania borja – Risso, p. 140, n. 348, pl. 9, fig. 132
1826 Alvania mediterranea Risso, p. 140, n. 349
1826 Alvania ferruginosa – Risso, p. 141, n. 352
1826 Alvania crassicostata – Risso, p. 143, n. 357
1826 Alvania sardea – Risso, p. 145, n. 366
1874 Rissoa peloritana – Aradas & Beinot, p. 205, pl. 4, fig. 16
1874 Rissoa nicolosiana – Aradas & Beinot, p. 206, pl. 4, fig. 14
1895 Rissoia (Turbella) discors v. miotaurinensis – Sacco, p. 22, fig. 51
1895 Rissoia (Turbella) discors v. perlonga – Sacco, p. 22, fig. 52
2011 Alvania discors – Chirli & Linse, p. 78, pl. 21, figs 3a-c
2021 Alvania discors – Chirli & Forli, p. 113, pls 90, 91, 92, figs B1-14, A1-20, A1-20
Stratigraphic distribution
Miocene – reported from Poland also how A. montagui, and from Italy. Pliocene – reported from Italy by Cocconi how R. montagui in Castell’Arquato; France and Cyprus. Pleistocene – Italy, Greece and Rhodes. Recent – Atlanto-mediterranean species, lives between the posidonia of the mud-detritus bottoms of the infralittoral zone.
References
Allan T. (1818). Sketch of the geology of the environs of Nice. Transactions of the Royal Society of Edinburgh 8(2): 427-464, pl. 8-10., available online at https://www.biodiversitylibrary.org/page/40639509
Chirli C. & Linse U. (2011). The Pleistocene Marine Gastropods of Rhodes Island (Greece). Tavarnelle, The authors. 447 pp.; 90 plates.
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Acknowledgements
Si ringrazia l’amico Carlo Chirli (Tavarnelle, Firenze) per la concessione all’uso di alcuni suoi testi. See also Edizioni Danaus
