Bittium merklini, Harzhauser & Guzhov & Landau, 2025

Bittium merklini sp. nov.

Figs 15A–E View FIGURE 15

Type material. Holotype PIN 5904 View Materials /20, SL: 5.4 mm, MD: 1.9 mm, Varivtsi ( Ukraine), Figs 15B View FIGURE 15 1 –B View FIGURE 1 4 View FIGURE 4 . Paratypes: PIN 5904 View Materials /19, SL: 5.6 mm, MD: 1.9 mm, Varivtsi ( Ukraine), Figs 15A View FIGURE 15 1 –A View FIGURE 1 2 View FIGURE 2 . PIN 5904 View Materials /21, SL: 6.2 mm, MD: 2.4 mm, Varivtsi ( Ukraine), Fig. 15C View FIGURE 15 . PIN 5904 View Materials /22, SL: 8.9 mm, MD: 2.6 mm, Lanivtsi ( Ukraine), Figs 15D View FIGURE 15 1 –D View FIGURE 1 2 View FIGURE 2 . PIN 5904 View Materials /23, SL: 5.5 mm, MD: 2 mm, Varivtsi ( Ukraine), Figs 15E View FIGURE 15 1 –E View FIGURE 1 2 View FIGURE 2 . All from late Badenian, Middle Miocene .

Type locality. Varivtsi ( Ukraine), Ukrainian Fore-Carpathian Basin .

Type stratum. Shelly sands.

Age. Middle Miocene, late Badenian.

Etymology. In honor of Roman L. Merklin, explorer of Neogene stratigraphy and bivalves of the Eastern Paratethys.

Diagnosis. Small or medium-sized, slender conical shell, with deeply incised suture, protoconch of 2.5 whorls with sinusigera, teleoconch whorls with four tuberculate spiral cords, changing from conical to subcylindrical during ontogeny, with varices on late whorls.

Description. Small or medium-sized, slender conical shell of 10–12 teleoconch whorls, attaining 6–9 mm in height, apical angle ~27–33°. Protoconch of 2.5 rounded whorls, with suprasutural thread and probably with wide-spaced microscopic pustules above. Protoconch with sinusigera (dp = 240–270 μm). Early teleoconch whorls convex, later whorls weakly convex to nearly straight-sided, separated by deeply incised suture. First nine whorls form conical teleoconch passing into subcylindrical outline, resulting in slender bullet-shaped outline. Sculpture of three primary cords, suprasutural cord largely obscured by next whorl. Two or three secondary spiral cords with pointed tubercles appear below suture: first secondary cord on second or third whorl, second secondary cord appears on seventh or eighth whorls, third cord may appear on tenth whorl. Second and third secondary spiral cords appear abapically to first secondary cord. Spiral cords almost equally spaced, crossed by 13–15 axial ribs bearing pointed tubercles. Microsculpture of numerous rows of tiny close-set pustules in spiral interspaces; numerous tiny pits over cords. Varices well developed, appearing from tenth whorl. Subsequent whorls with two varices per whorl, almost opposite each other. Last whorl about 35% of total height. Base strongly constricted, with two prominent peribasal cords and two or three thinner cords over fasciole. Aperture ovate. Columella excavated. Columellar callus forming thin, narrow rim, sharply delimited from base. Anal canal indistinct. Outer lip thin. Siphonal canal short and wide.

Discussion. Only one shell seems to be a fully grown, adult specimen ( Figs 15D View FIGURE 15 1 –D View FIGURE 1 2 View FIGURE 2 ), showing a characteristic bullet-shaped outline. This is confirmed by rare shells with teleoconchs of more than ten whorls, which show a comparable change in outline and sculpture transformation. This species is most close to Bittium praescabrum sp. nov. (late Badenian) and B. konkense Sokolov, 1899 (late Konkian), from which it differs in the flattish last two teleoconch whorls with two varices per whorl. It differs from Bittium praescabrum also in the late appearance of varices.

Distribution. Late Badenian (Middle Miocene) of the Central Paratethys.

Paleoenvironment. Shallow marine, inner neritic based on the associated fauna (own data A.G.).

Central Paratethys. Late Badenian (Middle Miocene): Ukrainian Fore-Carpathian Basin: Ripyntsi, Varivtsi (Khmel’nytskyi Region), Lanivtsi, Shushkivtsi (Ternopil Region), Plugiv (Lviv Region, Ukraine) (hoc opus) .