Blinia pseudolaevigata ( Sinzov, 1892 )

Anistratenko, Olga Yu., Bandel, Klaus & Anistratenko, Vitaliy V., 2006, A new genus of patellogastropod with unusual protoconch from Miocene of Paratethys, Acta Palaeontologica Polonica 51 (1), pp. 155-164 : 160-161

Blinia pseudolaevigata ( Sinzov, 1892)

Fig. 5B .

1892 Acmaea pseudolaevigata sp. nov.; Sinzov 1892: 63, pl. 3: 11–12.

1935 Acmaea pseudolaevigata ( Sinzov, 1892) ; Kolesnikov 1935: 128, pl.: 8–11.

1944 Acmaea soceni sp. nov.; Jekelius 1944: 42, pl. 2: 4–6 [partim, non figs. 1–3].

2000 Tectura pseudolaevigata ( Sinzov, 1892) ; Anistratenko 2000a: 33–39, pl. 2: 4a–4d.

Type material: The type material is not present in the collection of Museum of Odessa University where it was deposited by Sinzov (1892) and most probably lost .

Material.— Forty five specimens from middle Sarmatian of Letichev locality ( IGS NANU 41 /2004–60/2004) and lower Sarmatian of Shirokoe locality ( IGS NANU 32 /1999–58/ 1999), Ukraine .

Description.—The shell is small, thin, relatively tall−conical in all lateral views, oval in dorsal view. The apex is subcentral, tilted well backward, thus of sometimes hook−like appearance. The apical angle in anterior view varies from 60 ° to 70 °. The posterior slope is straight to slightly concave, the anterior slope usually somewhat convex. Sculpture consists of numerous, weak but clear radial ribs crossed by concentric lines of growth. The outer sculptured layer of a shell is usually peeled off so that the surface of teleoconch appears to be totally smooth. The aperture is moderately to broadly oval.

Specimens of Blinia pseudolaevigata from the middle Sarmatian of western Ukraine (Letichev) and the lower Sarmatian of southern Ukraine (Shirokoe) are characterized by round to oval pancake−like and almost flat protoconchs. The greater diameter of the embryonic shell (i.e., “pancake”) measures about 0.13–0.15 mm; it is situated symmetrically in the sagittal axis of the teleoconch. The surface of a protoconch may be smooth or wrinkled. Some specimens have a small pit in the top of their embryonic shell. The protoconch —early teleoconch transition is usually sharp, marked by a well−developed constriction or rim ( Fig. 5B 3 ).

Dimensions.—The shells studied measure up to 2.8 mm in length and up to 1.9–2.0 mm both in height and width. According to Kolesnikov (1935) the shells of Blinia pseudolaevigata can reach a larger size—up to 11.0 mm in length, 8.0 mm in width and 7.0 mm in height.

Discussion.— Blinia angulata differs by a lower shell and no backward tilt of the apex.

Two specimens of, perhaps, Blinia pseudolaevigata un− der the name Acmaea soceni Jekelius, 1944 have also been recorded by Harzhauser and Kowalke (2002: 62, pl. 12: 1–3) from the Sarmatian of St. Margarethen in the Vienna Basin ( Potamides disjunctus assemblage). The authors reported that the protoconch of the shell illustrated is separated from the teleoconch by a marked constriction and measures 0.3 mm in height (rather in diameter as shown by the figures and scale bar). Unfortunately the actual protoconch is not well preserved in their samples and can be identified with our material of Blinia pseudolaevigata with some doubts only. Moreover the dimensions of Blinia protoconchs in our material are smaller. Likewise the specimen of Acmaea soceni illustrated by Jekelius (1944) appears slightly higher in lateral view than that illustrated by Harzhauser and Kowalke (2002). Protoconchs of Acmaea soceni collected from the same locality as those described by Jekelius (1944) were documented. They are of the type as in Blinia and therefore Acmaea soceni is considered here as Blinia pseudolaevigata .

Stratigraphic and geographic range.— Blinia pseudolaevigata is a typical (in some localities abundant) and widespread species of early and middle Sarmatian sediments of the Eastern Paratethys viz. Ukraine, Moldova, Romania,

Central Sub−Caucasus to the Central Paratethys and its eastern shore at Soceni in Romania ( Kolesnikov 1935; Jekelius 1944; Anistratenko 2000a). It also perhaps is found in synchronous deposits of the western Central Paratethys (e.g., Švagrovský 1971; Harzhauser and Kowalke 2002).

Figures

Fig. 5. Blinia gen. nov. and Tectura Gray, 1847 from Miocene of Ukraine. A. Blinia angulata (d’Orbigny, 1844). Specimen (IGS NANU 1/2004) from the middle Sarmatian of Letichev, apical view (A1). Lateral view of the same specimen (A2). B. Blinia pseudolaevigata (Sinzov, 1892). Specimen (IGS NANU 41/2004) from the middle Sarmatian of Letichev, apical view (B1). Lateral view of the same specimen (B2). Detailed apical view of the embryonic shell and juvenile teleoconch of the same specimen as in B1 (B3). The embryonic shell is ornamented by fine concentric wrinkles and pit on the apex. C. Tectura zboroviensis (Friedberg, 1928). Specimen (IGS NANU 18/2003) from the Chokrakian of Yurkino, apical view (C1). Lateral and frontal views of the same specimen (C2, C3). Detailed apical view of the embryonic shell and juvenile teleoconch of the same specimen as in C1 (C4). The onset of juvenile teleoconch is ornamented by fine spiral threads. D. Blinia sp. Specimen (IGS NANU 4/2004) from the middle Sarmatian of Letichev. Detailed apical view of the embryonic shell and juvenile teleoconch.

Fig. 3. A sketch drawing of the inner shell surface of Blinia sp. with muscle scars indicated by arrows. Specimen (IGS NANU 88/2004) from the middle Sarmatian of Letichev. Anterior edge of a shell is on the top.