Theodisca azerbajdjanica K.A. Ali-Zade, 1940

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 : 81-83

Theodisca azerbajdjanica K.A. Ali-Zade, 1940 nov. comb.

Figs 11A–B

* Potamides azerbajdjanicus n. sp. —K.A. Ali-Zade 1940: 37, pl. 1, figs 11–14.

Potamides azerbajdjanicus Alz. var. semilaevigata n. var. —K.A. Ali-Zade 1940: 39, pl. 1, figs 15–19.

Potamides azerbajdjanicus Alz. —K.A. Ali-Zade 1954: 289, pl. 12, figs 22–26.

Potamides azerbajdjanicus var. semilaevigata Alz. —K.A. Ali-Zade 1954: 290, pl. 12, figs 27–28.

Cerithium subdisjunctum A. Ali-Zade et Kabakova n. sp. —A.A. Ali-Zade 1969: 153, pl. 48, figs 3–4.

Potamides caspius Andrus. — Dzhikiya 1977: 118, pl. 10, fig 7–11 [non Andrussow, 1902].

non Cerithium azerbaidjanicum [sic] (Alz.)—A.A. Ali-Zade 1969: 149, pl. 47, fig. 3 [= Potamides caspius Andrussow, 1902 ].

Type material. Lectotype designated herein: specimen illustrated in K.A. Ali-Zade (1954: pl. 12, fig. 22), no exact data about size are given: SL: ~ 23 mm, MD: ~ 7 mm, A.A. Ali-Zade (1969: 149) mentioned a lectotype but did not define a specimen. The specimen was stored in the Earth Science Museum at Moscow State University (The Museum of Natural History) but seems to be lost; Fig. 11A, reproduced from K.A. Ali-Zade (1954: pl. 12, fig. 22).

Type locality. Naftalan ( Azerbaijan) .

Stratigraphy. Late Pliocene/Pleistocene, Akchagylian.

Illustrated material. Lectotype of Potamides azerbajdjanicus semilaevigata K.A. Ali-Zade, 1940 , no exact data about size are given: SL: ~ 17 mm, MD: ~ 7 mm, Taribani Steppe area ( Georgia), Late Pliocene/Pleistocene, Akchagylian. The specimen was stored in the Earth Science Museum at Moscow State University (The Museum of Natural History) but seems to be lost; Fig. 11B, reproduced from Ali-Zade (1954: pl. 12, fig. 28).

Revised description. Small, slender conical to elongate pupoid shell of about nine teleoconch whorls; apical angle ~20–22°. Protoconch unknown. Early teleoconch whorls weakly convex, slightly angulated close above suture, with two weak spiral cords and prominent axial ribs. Later teleoconch whorls subcylindrical with weakly opisthocline or opisthocyrt axial ribs, fading out at various stages of growth. Adapical spiral cord forming faintly beaded adsutural spiral cord. Narrow spiral groove separating the subsutural cord from the rest of the shell. Weak beads may occur along abapical suture. Last whorl weakly convex to subcylindrical rapidly contracting into weakly convex base, with two prominent peribasal spiral cords. Aperture moderately wide, ovoid. Columella moderately excavated. Inner lip forming distinct rim, well demarcated from base with narrow pseudumbilicus. Anal canal indistinct. Outer lip not thickened, slightly flaring, shallowly opisthocyrt in lateral view. Siphonal canal weakly incised, short, slightly deflected to the left.

Discussion. Theodisca azerbajdjanica is coeval with the Mediterranean T. graeca ( Deshayes, 1832) . Therefore, it would be tempting to assume a close relation between both species to explain the Eastern Paratethyan occurrence of this species group. Nevertheless, T. azerbajdjanica differs from T. graeca in its slender outline and the densely spaced axial ribs on early whorls. Moreover, it lacks the prominent beads at the abapical suture, which are typical for T. graeca (see Brunetti 2013 for variability of T. graeca ). Overall, T. azerbajdjanica is much closer to T. biseriata ( Friedberg, 1914) in outline, but is distinguished from it by its axial sculpture. Theodisca etrusca ( Mayer, 1864) , from the Pliocene of the Mediterranean Sea, differs clearly in its prominent beads and the presence of a central spiral cord (see Brunetti 2013). Cerithium subdisjunctum A.A. Ali-Zade & Kabakova in Ali-Zade, 1969 seems to represent a morph with prominent axial sculpture.

Distribution. Theodisca azerbajdjanica was endemic in the Caspian Basin during the Late Pliocene, documented from eastern Georgia and Azerbaijan.

Eastern Paratethys. Akchagylian (Late Pliocene/Pleistocene): Caspian Basin: Chatma Lowland, Nazarlebi Mountains, Gorge Pantisharis-khevi, Taribani Steppe area ( Georgia) ( Ali-Zade 1954; Dzhikiya 1977), Eldari Steppe area, Naftalan ( Azerbaijan) ( Ali-Zade 1954, 1969).