Alvania (Alvania) oceani ( d’Orbigny, 1852 )

Kowalke, Thorsten & Harzhauser, Mathias, 2004, Early ontogeny and palaeoecology of the Mid-Miocene rissoid gastropods of the Central Paratethys, Acta Palaeontologica Polonica 49 (1), pp. 111-134 : 120

Alvania (Alvania) oceani ( d’Orbigny, 1852)

Fig. 7A .

Rissoa oceani sp. nov.; d’Orbigny 1852: 28, nr. 368. Rissoa Moulinsi d’Orbigny ; Hörnes 1856: 570, pl. 48: 14. Alvania curta ? var. rotundulina Sacco 1895: 24 (pars). Alvania oceani d’Orbigny ; Meznerics 1933: 330, pl. 13: 8a, b. Rissoa (Alvania) oceani d’Orbigny ; Strausz 1966: 72, textfig. 40. Alvania (Alvania) oceani (d’Orbigny) ; Bałuk 1975: 82, pl. 9: 17. Alvania (Alvania) oceani (d’Orbigny) ; Svagrovský 1981: 116, pl. 36:

1–3. Alvania (Alvania) oceani (d’Orbigny) ; Atanackovic 1985: 86, pl. 20:

11, 12.

Material.— Fifteen specimens from the Badenian of Steinebrunn , Lower Austria, NHMW 2002 z0030/0012.

Description.—The small, elongate, egg−shaped shell comprises 5–6 slightly rounded whorls measuring up to 3 mm in height. The last whorl forms about 60–70% of total shell height. Teleoconch sculpture consists of 20 straight axial ribs crossed by 6 about equally strong spiral cords, forming a very regularly reticulate pattern. The base is sculptured by 6 spiral cords. The thickened, egg−shaped aperture is characterised by a faint anterior notch and by a pointed posterior portion. The columellar edge is bent.

The protoconch comprises 2.5 slightly rounded whorls measuring 0.33 mm in height and 0.35 mm in width. Sculpture is not preserved. The first whorl measures about 0.04 mm in the width of the initial cap and 0.15 mm in maximum diameter. The transition from the embryonic shell to the larval shell is indistinct due to the poor preservation. The protoconch is terminated by a slightly thickened, fractionated sinusigera notch.

Remarks.— Alvania (Alvania) oceani differs from the similar species A. (A.) venus by its finer sculpture, comprising 4 axial ribs more, and by its considerably smaller protoconch which in addition comprises 0.25 whorls less.

A. (A.) oceani is commonly found in the Badenian of the entire Central Paratethys and was variously mentioned from Poland, Hungary, Ukraine, Bosnia, Slovakia, and Austria. Outside the Paratethys the species is described by Cossmann and Peyrot (1919) from the Early Miocene of SW France. There, also the oldest occurrence was mentioned from the Late Oligocene by Lozouet (1986).

Figures

Fig. 7. Four species of Alvania (Alvania) Risso, 1826. A. Alvania (Alvania) oceani (d’Orbigny, 1852). Specimen (NHMW 2002z0030/0012) from the Badenian of Steinebrunn, Lower Austria (A1). Protoconch of the same specimen as in A1 in lateral view (A2). The protoconch is terminated by a slightly thickened, fractionated sinusigera notch. B. Alvania (Alvania) perregularis (Sacco, 1895). Specimen (NHMW 2002z0030/0013) from the Early Badenian of Sedlec/Nový Rybník, Czech Republic (B2). Lateral and apical view of the protoconch of the same specimen as in B2 (B1, B3). The protoconch is terminated by a sinusigera notch. Detailed apical view of the initial whorl of the same protoconch as in B3 (B4). The embryonic shell consists of one inflated whorl, which is terminated by a thickened rim, reflecting the thickened apertural margin of the hatchling. C. Alvania (Alvania) transiens (Sacco, 1895). Specimen (NHMW 2002z0030/0014) from the Badenian of Steinebrunn, Lower Austria (C1). Protoconch of the same specimen as in C1 in lateral and apical view (C2, C3). The larval shell is sculptured by spiral rows of tubercles.It is terminated by a well developed sinusigera notch. D. Alvania (Alvania) schwartzi (Hörnes, 1865). Specimen (NHMW 2002z0030/0015) from the Badenian of Steinebrunn, Lower Austria (D2). Lateral and apical views of the protoconch of the same specimen as in D2 (D1, D3, D4). The protoconch is terminated by a well developed sinusigera notch. Detailed view of the initial whorl of the same protoconch as in D4 (D5). The embryonic shell is demarcated from the subsequent larval shell by a thickened rim.