Bittium bosphoranum ( Andrussow, 1890 )

Bittium bosphoranum ( Andrussow, 1890)

Figs 6A–H View FIGURE 6

* Cerithium bosphoranum sp. nov. — Andrussow 1890: 299, pl. 4, fig. 10.

Cerithium (Bittium) bosphoranum Andrus.— Andrussow 1906: 397 .

Cerithium bosphoranum Andrus.— Davidaschvili 1931: 20 , pl. 4, fig. 9.

Bittium bosphoranum Andrusssov, 1890 — Zelinskaya et al. 1968: 162, pl. 39, fig. 27.

Bittium reticulatum View in CoL (Costa)— Iljina 1972: 49, pl. 1, figs 7–8 [non Bittium reticulatum View in CoL ( da Costa, 1778)].

Bittium reticulatum View in CoL (Costa)— Iljina et al. 1976: 87, pl. 25, figs 11–18 [non Bittium reticulatum View in CoL ( da Costa, 1778)].

Bittium reticulatum View in CoL (Costa)— Badzoshvili 1979: 27, pl. 19, figs 9–14, pl. 20, fig. 1 [non Bittium reticulatum View in CoL ( da Costa, 1778)]. Bittium reticulatum View in CoL (Costa)— Badzoshvili 1986: 36, 62, pl. 18, figs 1–4 [non Bittium reticulatum View in CoL ( da Costa, 1778)].

Type material. The shell illustrated in Andrussow 1890 not marked in his collection, lectotype (designated herein): SPSU 50/150-1; SL: 6 mm, MD: 2.3 mm, Figs 6A View FIGURE 6 1 –A View FIGURE 1 2 View FIGURE 2 . Paralectotypes: SPSU 50/150-2 ; SL: 5.9 mm, MD: 2.2 mm, Figs 6B View FIGURE 6 1 –B View FIGURE 1 2 View FIGURE 2 . SPSU 50/150-3; SL: 5.9 mm, MD: 2.2 mm, Fig. 6C View FIGURE 6 . Also 13 unfigured paralectotypes under number SPSU 50/150. All specimens from Mount Mitridat, Kerch (Crimea), early Maeotian , Late Miocene .

Illustrated material. PIN 2220/292; SL: 6.7 mm, MD: 2.5 mm, Gup (= Gupi) (Abkhazia), illustrated in Iljina et al. (1976: pl. 25, fig. 13), Figs 6D View FIGURE 6 1 –D View FIGURE 1 2 View FIGURE 2 . PIN 2220/502; SL: 6.9 mm, MD: 2.2 mm, Pshish River near Erivanskii ( Russia), illustrated in Iljina et al. (1976: pl. 25, fig. 15), Fig. 6E View FIGURE 6 . PIN 5904/1; SL: 6.5 mm, MD: 2.1 mm, Gup (Abkhazia), Figs 6F View FIGURE 6 1 –F View FIGURE 1 2 View FIGURE 2 . PIN 5904/3, Galidzga River (Abkhazia), Figs 6G View FIGURE 6 1 –G View FIGURE 1 3 View FIGURE 3 . PIN 5904/2, SL: 4.4 mm, MD: 1.4 mm, Lake Tobechik (Crimea), Fig. 6H View FIGURE 6 .

Description. Medium sized, moderately slender conical shell of 9–10 teleoconch whorls, attaining 7–8.5 mm in height; apical angle 19–35°. Protoconch of 2.5–3.0 whorls, terminal part angled mid-whorl, with sinusigera (dp = ~270 μm). Early teleoconch whorls weakly angled with broad subsutural ramp, later whorls convex. Suture deeply incised, weakly undulating. First teleoconch whorl with two prominent primary spiral cords placed mid-whorl and partially visible suprasutural cord. First secondary cord appears on subsutural ramp on third whorl. Next secondary spiral cord appears below first secondary cord and additional cord may appear along abapical suture. Last whorl with five, rarely four, subequal prominent spiral cords, separated by about 1.5 times wider interspace. Axial ribs appear on first or second teleoconch whorls; 14–18 axial ribs on penultimate whorl plus varices. Spiral cords tuberculate at intersections with densely spaced, prominent axial ribs, separated by narrower interspaces. Two or more varices on last whorl, occurring at between 160–180 °to each other, strengthening during ontogeny; occasionally axially aligned. Second half of last whorl typically devoid of axial ribs, bearing only wide-spaced varices and smooth spiral cords. Microsculpture of spiral rows of tiny pustules, spiral cords with tiny pits. Later teleoconch whorls convex with periphery below mid-whorl. Last whorl convex, moderately constricted, attaining about 37–41% of total height. Base with two prominent peribasal spiral cords, three weaker cords over fasciole. Aperture wide and ovate. Columella weakly excavated. Columellar callus forming thin, narrow rim. Anal canal indistinct, wide. Outer lip thin. Siphonal canal short and very wide.

Discussion. This species is characterized by its peculiar sculpture of prominent spiral cords with small tubercles developed at axial intersections and by the broad, prominent varices, which are slightly reminiscent of some Potamididae such as Terebralia . This similarity was already stressed by Andrussow (1890), but his illustration was very schematic. Iljina (1972), Iljina et al. (1976) and Badzoshvili (1979) identified these Maeotian shells as Bittium reticulatum ( da Costa, 1778), which is more slender, has a less incised suture and has weaker varices than Bittium bosphoranum ( Andrussow, 1890) .

Some samples contain B. bosphoranum with more slender shells and reduced axial sculpture and weak tubercles ( Figs 6C, G View FIGURE 6 2 View FIGURE 2 ). These specimens are transitional to B. acutum Ossaulenko, 1936 , which is probably a descendant of B. bosphoranum . Bittium acutum differs in its reduced axial sculpture, the weaker and more wide-spaced beads, the reduced varices, the distinction between secondary and primary cords, and the usually angled whorls.

Paleoenvironment. Unknown.

Distribution. Only known from early Maeotian (Late Miocene) of the Eastern Paratethys.

Eastern Paratethys. Early Maeotian (Late Miocene): Black Sea Lowland : Yagorlyts’kyi Kut peninsula (where was former Svobodnyi Port) (Kherson Region); Crimea: Nasyr, Kerch (including Mount Mitridat), Semenovka, Lake Tobechik, Zavetnoe (Crimea, Russia). Ciscaucasia : Anapa District (boreholes), Apchas river near Kutais, ravine Belaya Saklya (Pshish river), Erivanskii, ravine Kordashova (Pshish river), capes Panagiya and Popov Kamen’, Shebsh river near Grigor’evskaya, Sheptal’skii, Taman’ (Krasnodar Krai, Russia), Sulak river near Bavtugai (Dagestan, Russia); Transcaucasia : Galidzga River near village Gup (or Gupi), Otap River (Abkhazia); Transcaspian Region: Cape Urdek ( Iljina et al. 1976; Badzoshvili 1979; hoc opus).