Alvania littorinoides

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Alvania littorinoides
Alvania littorinoides 001.jpg
Shell of Alvania littorinoides (holotype at MNHN, Paris)
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Mollusca
Class: Gastropoda
Subclass: Caenogastropoda
Order: Littorinimorpha
Superfamily: Rissooidea
Family: Rissoidae
Genus: Alvania
Species:
A. littorinoides
Binomial name
Alvania littorinoides
Cossmann, 1921

Alvania littorinoides is an extinct species of minute sea snail, a marine gastropod mollusc or micromollusk in the family Rissoidae. [1]

Contents

Description

The length of the shell attains 2.25 mm, its diameter 1.5 mm.

(Original description in French) The shell is minute and fragile. The spire is moderately elongated and exhibits a conical form, culminating in a smooth, obtuse protoconch. Five scalariform, convex whorls ascend rapidly, attaining approximately two-thirds of the maximum shell width. These whorls are characterized by a sloping ramp above the linear suture, and each bears three spiral keels that are decussated by growth lines. Additionally, the lower ramp is finely striated. The body whorl constitutes approximately half the total shell height, displaying a slightly convex profile and ornamentation similar to the spire. The base is rounded, sloping gently or remaining nearly flat, and exhibits a central excavation without forming a true umbilicus. The columella is barely detached, and the entire shell surface is adorned with six to seven fairly regularly spaced ribs, less prominent than the keels observed on the body whorl. The aperture is circular, possessing a thin, slightly inclined outer lip with a weakly defined external border. The columella is excavated, exhibiting a narrow, non-callous external border that does not reflect onto the basal depression. [2]

Distribution

Fossils of this species were found in Pliocene strata in Lower Normandy, France.

References

  1. MolluscaBase eds. (2024). MolluscaBase. Alvania littorinoides Cossmann, 1921 †. Accessed through: World Register of Marine Species at: https://www.marinespecies.org/aphia.php?p=taxdetails&id=881481 on 2024-02-01
  2. Cossmann, M. (1921). Essais de paléoconchologie comparée. Douzième livraison. Paris: (the author). 349 pp., plates A-D, 1-6 PD-icon.svg This article incorporates text from this source, which is in the public domain .