Alvania (Alvania) perregularis (Sacco, 1895)

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 : 120-121

Alvania (Alvania) perregularis (Sacco, 1895)

Fig. 7B .

Rissoa Mariae d’Orbigny ; Hörnes 1856: 563, pl. 48: 9a, b.

Alvania Mariae ? var. perregularis ; Sacco 1895: 25.

Alvania (Acinus) perregularis Sacco ; Meznerics: 331, pl. 13: 9a, b.

Alvania perregularis Sacco ; Bohn−Havas 1973: 1037, pl. 3: 1, 2.

Alvania (Turbona) perregularis (Sacco) ; Bałuk 1975: 85, pl. 9: 13–15.

Alvania (Turbona) perregularis (Sacco) ; Svagrovský1981: 118,pl.36: 4.

Alvania (Alvania) perregularis (Sacco) , Atanackovic 1985: 87, pl. 20: 17, 18.

Material.— Nine specimens from the Badenian of Sedlec / Nový Rybník (formerly Porz) 6 km SE of Mikulov, Czech Republic, NHMW 2002 z0030/0013.

Description.—The elongated, egg−shaped shell consists of 6 flat whorls measuring up to 3 mm in height. The last whorl forms about 70% of total shell height. The teleoconch sculpture consists of a very regular reticulate pattern of 24–30 straight to slightly prosocline axial ribs crossed by 8–10 spiral cords. Nodes form in the points of intersection of the axial and spiral sculpture. The large aperture has a drop shape. It is characterised by a faint, broad anterior notch and by a pointed, slightly incised parietal portion. The interior portion of the outer and basal lip bears 10–11 coarse teeth.

The protoconch comprises 2.75 slightly rounded whorls measuring 0.46 mm in height and 0.45 mm in maximum diameter. The embryonic shell consists of one inflated whorl measuring 0.06 mm in the width of the initial cap and 0.17 mm in maximum diameter. Embryonic sculpture consists of 10 rows of granulated spiral threads. The transition to the subsequent larval shell is indicated by a thickened rim on the shell. The larval shell is characterised by remains of 8 rows of coarse granules and is terminated by a sinusigera notch. The onset of the teleoconch is indicated by the formation of the regular adult sculpture.

Remarks.—The protoconch resembles that of Alvania (Alvania) ampulla regarding the sculpture of the larval shell, but differs by its much larger size and by comprising 0.75 larval whorls more. Additionally, the embryonic sculpture is much coarser in the case of A. perregularis .

Alvania (Alvania) perregularis represents an ubiquitous species during the Badenian of the Central Paratethys. Literature data cover an area from Poland and Ukraine, via Austria, Hungary, and Romania south to Bosnia and Bulgaria (see Strausz 1966; Atanackovic 1985).

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.