Thericium zhizhchenkoi, Harzhauser & Guzhov & Landau, 2025

Thericium zhizhchenkoi sp. nov.

Figs 62A–B View FIGURE 62

Cerithium rubiginosum Eichwald— Zhizhchenko 1936: 198 , pl. 21, figs 18–20.

Cerithium rubiginosum Eichwald— Zhizhchenko 1959: 248 , pl. 16, figs 29–31.

Type material. Holotype. TSNIGR 150 /11330, SL: 18 mm, MD: 9 mm, Belomechetskaya ( Russia), Middle Miocene, early Chokrakian, Figs 62A View FIGURE 62 1 –A View FIGURE 1 2 View FIGURE 2 . Paratype. PIN 5904 View Materials /65, SL: 16.2 mm, MD: 7.5 mm, Novo-Kuvinsk ( Russia), Middle Miocene, early Chokrakian, Figs 62B View FIGURE 62 1 –B View FIGURE 1 2 View FIGURE 2 .

Type locality. Belomechetskaya ( Russia), Ciscaucasia .

Type stratum. Unknown.

Age. Middle Miocene, early Chokrakian (Langhian).

Etymology. Referring to Russian geologist Boris Zhizhchenko (1907–1983), who firstly found this species.

Diagnosis. Small sized, stout conical shell characterized by a dense spiral sculpture with three broader rows of rounded nodes, without varices. Middle row partly with spiny nodes, forming periphery at mid-whorl.

Description. Small, stout conical shell of about eight teleoconch whorls; apical angle 35–39°. Protoconch unknown. Spire whorls low, with mid-whorl angulation, covered by densely spaced cords delimited by narrow furrows, with two broad band-like cords with rows of nodes (12–14 on last whorl) placed at adapical suture and at mid-whorl. Tubercles mid-whorl more prominent, spiny. Two weaker spiral bands between suture and adapical broad cord, three thinner band-like cords between broad spiral cords, five to six cords between mid-whorl broad cord and abapical suture. Axial sculpture indistinct, vague axial ribs below mid-whorl angulation, fading over concave subsutural ramp. Suture moderately incised, shallowly undulating. Last whorl slightly inflated, attaining ~55% of total height, with strongly constricted base delimited by broad peribasal band with low round nodes or poorly developed swellings. Base covered by close-set spiral cords and threads with two cords more prominent, dividing base into three parts. Aperture ovate. Columella broadly and strongly excavated; columellar callus thin. Anal canal weakly incised and clearly constricted by parietal denticle. Outer lip thickened. Siphonal canal well developed, deeply incised, only slightly deflected to the left.

Discussion. The holotype of Thericium zhizhchenkoi is the most complete specimen with complete aperture but is slightly abraded and its sculpture is poorly preserved; especially the spiny character of the tubercles at mid-whorl is missing. Shells from other localities have high, pointed tubercles at mid-whorl, and the round nodes of the abapical cord significantly lower and sometimes reduced up to indistinct, flattened elevations. This species is closely similar to Thericium vovkotrubense sp. nov., for comparison see that species.

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

Distribution. A rare species documented from the earliest Chokrakian of the Ciscaucasian area of the Eastern Paratethys Sea.

Eastern Paratethys. Early Chokrakian (Middle Miocene): Ciscaucasia : Belaya River (Adygea), Novo-Kuvinsk (Karachay-Cherkessia), Khadyzhensk (Krasnodar Krai), Belomechetskaya (Stavropol Krai, Russia) ( Zhizhchenko 1936; hoc opus) .