Potamides galidzgensis (Iljina, 1976)

Harzhauser, Mathias, Guzhov, Aleksandr & Landau, Bernard, 2023, A revision and nomenclator of the Cainozoic mudwhelks (Mollusca: Caenogastropoda: Batillariidae, Potamididae) of the Paratethys Sea (Europe, Asia), Zootaxa 5272 (1), pp. 1-241 : 73-75

Potamides galidzgensis (Iljina in Iljina, Nevesskaja & Paramonova, 1976)

Figs 9A–C

Pirenella sp. — Iljina 1972: pl. 1, figs 9–11.

* Pirenella galidzgensis L. Iljina — Iljina et al. 1976: 218, pl. 27, figs 18–22.

Pirenella disjuncta (Sow.) — Badzoshvili 1979: 27, pl. 19, figs 1–3 [non J. de C. Sowerby, 1832].

Pirenella galidzgensis L. Iljina — Badzoshvili 1986: 27, pl. 17, figs 7–8.

Type material. Holotype, PIN 2220/293, SL: 13.8 mm, MD: 6.0 mm, Galidzga River near village Gup ( Russia, Abkhazia), early Maeotian, illustrated in Iljina (1972, pl. 1, fig. 9, as Pirenella sp. ; Iljina et al., 1976, pl. 27, fig. 18) ( Fig. 9A).

Type locality. Galidzga River near Gup (Abkhazia) .

Stratigraphy. Late Miocene, early Maeotian.

Illustrated material. PIN 5872/1, SL: 15.1 mm, MD: 6.6 mm, Galidzga River near village Gup ( Russia, Abkhazia), early Maeotian ( Figs 9B 1 –B 2). PIN 5872/4, SL: 4.05 mm, MD: 1.95 mm, Galidzga River near village Gup ( Russia, Abkhazia), early Maeotian ( Fig. 9C).

Revised description. Small (15 mm in height), moderately low conical shell of about ten teleoconch whorls; apical angle ~38°. Protoconch unknown. Early teleoconch whorls convex with incised suture and two prominent, beaded spiral cords initially at mid-whorl, but later moving close to abapical suture. Third spiral cord appears below adapical suture on mid-teleoconch whorls and quickly becomes equal in strength. Later teleoconch whorls with three prominent equal spiral cords with rounded beads (14–17 on last whorl). Delicate spiral striae between beads on early teleoconch whorls. Whorl profile usually convex. Last whorl with flattened periphery and convex base, bearing three primary rows of tubercles, a fourth narrower row appearing at the level of the insertion of the outer lip on the last whorl, four further subobsoletely beaded cords over base. Aperture subquadrate-rounded. Columella excavated, smooth. Aperture not preserved.

Discussion. Herein, we treat Potamides galidzgensis as a geographically restricted offshoot of Potamides taitboutii (d’Orbigny, 1844) . Potamides galidzgensis differs from P. taitboutii in its smaller and broader shell, its reticulate sculpture, and the higher number of axial ribs. Potamides galidzgensis forms populations with typical and stable morphology in the region of Abkhazia (South Caucasus). There, it can be clearly separated from Potamides taitboutii , which is found only in few levels, mostly represented by morphs with reduced sculpture. At the same time, transitional morphs of P. taitboutii , which are close to P. galidzgensis occur in several samples from Western Ciscaucasia. Transitional morphs are also common in samples from Krasnodar Krai and are documented by A.G. from one sample from Kerch (locality Staryi Karantin). Thus, the transition from Potamides taitboutii into P. galidzgensis can be traced in Ciscaucasia.

River near village Gup ( Russia, Abkhazia), early Maeotian. B 1 –B 2. Potamides galidzgensis (Iljina in Iljina, Nevesskaja & Paramonova, 1976), PIN 5872/1, Galidzga River near village Gup ( Russia, Abkhazia), early Maeotian. C. Potamides galidzgensis

(Iljina in Iljina, Nevesskaja & Paramonova, 1976), PIN 5872/4, Galidzga River near village Gup ( Russia, Abkhazia), early

Maeotian.

For Transcaucasia very little information is available on occurrences of Potamides . After Kolesnikov (1940: 363) some researchers mentioned P. disjunctoides (= P. taitboutii ), while others wrote about Potamides close to taitboutii from the Azerbaijan Maeotian. For example, the specimen of P. galidzgensis described herein from the Krasnodar Krai, was originally labeled as Cerithium sp. nov. by A.A. Steklov in his collections. Therefore, records of “ disjunctoides ” and “close to disjunctoides ” from Azerbaijan might rather represent P. galidzgensis . Unfortunately, no specimens from that territory have ever been illustrated and no material is available in the collections studied by us.

Distribution. Potamides galidzgensis lived in the Eastern Paratethys (western Ciscaucasia and Transcaucasia ) during the early Maeotian.

Eastern Paratethys. Early Maeotian (Late Miocene): Crimea: Kerch; Ciscaucasia: Kutais, Pshish River near Kabardinskaya, Shebsh River near Grigor'evskaya, Tsitse River (Krasnodar Region, Russia) (own data); Transcaucasia: Galidzga River near Gup, Gedzhiri River (Abkhazia) ( Badzoshvili 1979; own data).