Bittium konkense Sokolov, 1899

Bittium konkense Sokolov, 1899

Figs 13A–O

* Bittium reticulatum da View in CoL Costa var. konkensis — Sokolov 1899: 37, 80, pl. 4, figs 25–30.

Cerithium konkensis Sok.— Ossipov 1932: 66 , pl. 4, figs 10–12.

Cerithium konkensis Sok. var. sokolovi n. var. — Ossipov 1932: 67, pl. 4, fig. 13.

Bittium moesiense n. sp. — Jekelius 1944: 82, pl. 21, figs 18–20.

Cerithium konkensis Sokol.— Zhgenti 1958: 83 .

Cerithium konkensis Sok.— Gamkrelidze et al. 1964: 273 .

Cerithium konkensis Sok. var. sokolovi Ossip. — Gamkrelidze et al. 1964: 274 .

Bittium konkensis Sokolov, 1899 — Zelinskaya et al. 1968: 163, pl. 40, figs 3–4.

Bittium reticulatum deforme (Eichw.) — Zhgenti 1991: 72, pl. 40, figs 1–8 [non Bittium deforme ( Eichwald, 1829) ]. Bittium (Bittium) reticulatum View in CoL ( Costa, 1778)— Iljina 1993: 67, pl. 8, figs 8–9 [non Bittium reticulatum View in CoL ( da Costa, 1778)]. Bittium (Bittium) spina (Partsch, 1842) — Iljina 1993: 69 (pars), pl. 8, figs 16–19 [non Bittium spina ( Hörnes, 1855) ]. Bittium (Stylidium) amitrovi L. Iljina View in CoL , sp. nov. — Iljina 1993: 70, pl. 8, figs 20–21.

Bittium (Stylidium) amitrovi View in CoL L. Il’jina, sp. nov.— Iljina 1994: 36, pl. 1, figs 10–11.

Bittium sp. — Ilgar 2015: 69, text fig. 5(B), fig. 15.

non Bittium reticulatum konkensis Sok.— Kókay 1985: 94 , pl. 9, fig. 13 [= Bittium sp. ].

non Bittium moesiense Jekelius, 1944 — Bandel 2006: 72, pl. 5, figs 7–8 [? = Bittium orientale ( Andrussow, 1911) ].

Type material. Lectotype designated herein: TSNIGR 468/302, SL: 8 mm, MD: 2.5 mm, Figs 13A 1 –A View FIGURE 1 2 View FIGURE 2 , illustrated in Sokolov 1899, pl. 4, fig. 28. Paralectotypes: TSNIGR 477/302, SL: 6 mm, MD: 2.2 mm, Fig. 13B. TSNIGR 473/302, SL: 6.5 mm, MD: 2.5 mm, Fig. 13C. TSNIGR 471/302, SL: 7.3 mm, MD: 2.6 mm, Fig. 13D. All specimens from Yul’ivka ( Ukraine), Middle Miocene, late Konkian. The type series of Bittium konkense contains 19 shells and is stored in the TSNIGR Museum. A part contains specimens marked as shells illustrated in Sokolov (1899) (numbers from 465/302 to 470/302). The second part contains unfigured shells (numbers 471/302–483/302). All shells come from the type locality. We compared the specimens marked as illustrated types with enlarged photos in Sokolov (1899) and found that most do not correspond to the figures. Only 468/302 (with crushed aperture after comparison) and 470/302 can be identified as illustrated types. Moreover 470/302, which is marked in the collection as specimen of Sokolov (1899, pl. 4, fig. 30), seems to represent his fig. 26. Sokolov’s figure 25 is too small to be identified with certainty. No other illustrated specimens could be identified in the second lot.

Illustrated material. PIN 4450/182, SL: 6.4 mm, MD: 2.4 mm, holotype of Bittium amitrovi Iljina, 1993 , Aksengir Mountain ( Kazakhstan), Middle Miocene, late Konkian, Fig. 13E. PIN 5904/27, SL: 5.2 mm, MD: 2.1 mm, Karatyulei ( Kazakhstan), Middle Miocene, late Konkian, Fig. 13F. PIN 5904/13, SL: 5.7 mm, MD: 2 mm, Aksengir Mountain ( Kazakhstan), Middle Miocene, late Konkian, Fig. 13G. Lectotype of Bittium konkense var. sokolovi Ossipov, 1932 (refigured from Sokolov 1899, pl. 4, fig. 30), Yul’ivka ( Ukraine), Middle Miocene, late Konkian, Fig. 13H. PIN 5904/24, SL: 4.5 mm, MD: 1.5 mm, gully Chumnaya ( Russia), Middle Miocene, late Konkian, Fig. 13I. PIN 5904/25, SL: 4.3 mm, MD: 1.7 mm, gully Chumnaya ( Russia), Middle Miocene, late Konkian, Fig. 13J. PIN 5904/28, SL: 4.3 mm, MD: 1.6 mm, Bursuc ( Moldova), Middle Miocene, latest Badenian, Fig. 13K. PIN 5904/26, SL: 4.4 mm, MD: 1.9 mm, Aksengir Mountain ( Kazakhstan), Middle Miocene, late Konkian, Fig. 13L. PIN 5904/31, SL: 9 mm, MD: 2.9 mm, Kiyandy ( Kazakhstan), Middle Miocene, late Konkian, Fig. 13M. PIN 5904/32, SL: 9.6 mm, MD: 3.2 mm, Kiyandy ( Kazakhstan), Middle Miocene, late Konkian, Fig. 13N. Holotype of Bittium moesiense Jekelius, 1944 (refigured from: Jekelius 1944, pl. 21, fig. 18), SL: 4 mm, MD: 1.4 mm, Soceni ( Romania), Middle Miocene, Volhynian, Fig. 13O. PIN 5904/29, SL: 3.6 mm, MD: 1.3 mm, Bursuc ( Moldova), Middle Miocene, latest Badenian, Fig. 13P. PIN 5904/30, SL: 5 mm, MD: 1.9 mm, Bursuc ( Moldova), Middle Miocene, latest Badenian, Fig. 13Q.

Revised description. Small, slender, conical shell of 10–12 teleoconch whorls, attaining about 6–8 mm in height; apical angle 21–25°. Protoconch unknown. Teleoconch whorls weakly convex or faintly angled at mid-whorl. Suture deeply incised. First three whorls with two prominent spiral cords near mid-whorl crossed by increasingly more prominent axial ribs. Third primary cord along abapical suture. First secondary cord appears subsuturally on fourth teleoconch whorl. Second secondary cord appears below the first one or two whorls later or may be absent. Axial ribs with rounded tubercles at intersections with cords. Axial ribs may be reduced at various ontogenetic stages, partly resulting in shells with spiral cords without beads. Microsculpture represented by numerous rows of densely spaced pustules arranged in interspaces between spiral cords. Adult shells often with prominent varix close to aperture, second less prominent varix may occur at beginning of last whorl. Occasionally with up to two distinct varices per whorl. Spire whorls convex, with periphery at mid-whorl. Last whorl convex, moderately constricted, attaining 35–43% of total height. Base with two peribasal cords, the upper one stronger, and up to five narrower spiral cords over base and fasciole. Aperture moderately wide, ovate. Columella excavated. Columellar callus forming thin, narrow rim. Anal canal indistinct. Outer lip thin. Siphonal canal very short, wide, shallow.

Synonyms. Bittium moesiense Jekelius, 1944 , from the Sarmatian (Volhynian) of Soceni ( Romania). We tentatively treat this species as Sarmatian occurrence of Bittium konkense as we do not see convincing differences to separate the two. We have several shells coming from the uppermost Badenian sample of Bursuc ( Moldova), which are close to Bittium konkense with rare secondary cords. Ossipov (1932) treated the specimen illustrated by Sokolov (1899: pl. 4, fig. 30) as his new Cerithium konkensis var. sokolovi , based on its reduced axial sculpture.

Herein, we synonymize Bittium amitrovi Iljina, 1993 with Cerithium konkensis var. sokolovi Ossipov 1932 . The type material of Bittium amitrovi is represented by rounded shells with worn sculpture, but we observe poorly visible axial elements, which are strongly reduced on the last whorls. We have studied the shells, which Iljina treated as Bittium amitrovi in her collection. These are worn shells in all cases, partially with visible axial sculpture on early whorls or even on all whorls of less worn shells. The type series of Bittium konkense documents a broad variability in sculpture ranging from prominent axial ribs on the entire teleoconch to specimens almost devoid of ribs. Therefore, Cerithium konkensis var. sokolovi and Bittium amitrovi are cases of intraspecific variability of Bittium konkense . Shells with reduced axial sculpture are typical for the type locality and in the Transcaspian region, but unknown from Ciscaucasian localities. This might have ecological reasons.

Discussion. Bittium konkense Sokolov, 1899 from Kiyandy ravine ( Figs 13M–N) differs from other specimens of this species in the more slender shells composed of more numerous whorls. Shells from this locality vary from morphs as illustrated in Sokolov (1899, pl. 4, fig. 28) and Iljina (1993, pl. 8, figs 17, 19) to shells, having 12 to 14 whorls and attaining up to 14 mm in height. The last whorls may be convex or flattened. Overall, B. konkense is highly variable in size and shape from various localities of the Eastern Paratethys. Typically, it is smaller at Caucasian localities than at Transcaspian localities and the type area.

This species was confused by Iljina (1993) with the extant B. reticulatum ( da Costa 1778) and was originally established as subspecies of that species. Bittium konkense differs from B. reticulatum in its cancellate sculpture, the subobsolete varices, the more constricted base, and the prominent adapical peribasal spiral cord. Bittium grinzingense sp. nov. is reminiscent of B. konkense in its convex whorls but is more slender and has pricky beads. Bittium konkense is close to B. merklini sp. nov., which might be a possible ancestor. Bittium konkense differs in its convex adult whorls with poorly developed varix only close to the aperture, whereas Bittium merklini has comparatively straight-sided whorls and two well developed varices on the last three whorls.

Bandel (2006) illustrated a juvenile shell as Bittium moesiense Jekelius, 1944 from Bulganak (Crimea), probable meaning Bulganak Bay, without stratigraphic information. This specimen has a broad subsutural ramp and only two spiral cords on the fourth teleoconch whorl and therefore is not conspecific with Bittium moesiense / konkense . The specimen might rather represent the early Chokrakian Bittium orientale ( Andrussow, 1911) .

Paleoenvironment. Shallow marine foreshore based on sedimentology and associated fauna (own data A.G.).

Distribution. Latest Badenian and Volhynian of the Central Paratethys Sea, and late Konkian (Middle Miocene) of the Eastern Paratethys Sea.

Eastern Paratethys. Late Konkian (Middle Miocene): Black Sea Lowland : Yul’ivka (Zaporizhzhia Region, Ukraine) ( Sokolov 1899). Ciscaucasia : Chumnaya and Vertepnaya gullies (Adygea), Pivol’nyi (= so named Mount Dubrovaya) (Stavropol Krai, Russia); Transcaucasia : Saberno (= Papynrkhua) (Abkhazia), Agara, ravine Natsvaltskhali (near Mount Saryyal), Tbilisi (ravine Khevdzmari, district Gldani) ( Georgia); Transcaspian Region: Aksengir Mountain, to west of saline Karatuley, ravine Kiyandy, well Molakuduk, place Mynsualmas (Mangystau Region, Kazakhstan) (Zghenti 1958; Iljina 1993; hoc opus).

Central Paratethys. Late Badenian (Middle Miocene): Moldavian Platform: Bursuc ( Moldova) (hoc opus). Sarmatian (Volhynian): Transylvanian Basin: Soceni ( Romania) ( Jekelius 1944).