Theodisca cicur ( Zhizhchenko, 1934 ) Harzhauser & Guzhov & Landau, 2023

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 : 88-89

Theodisca cicur ( Zhizhchenko, 1934) nov. comb.

Figs 13A–K

Cerithium truncatum sp. nov. — Baily 1858: 150, pl. 10, figs 11a–b [non Gray in Griffith & Pidgeon, 1833, non Griffith &

Pidgeon, 1834]. Cerithium cf. nodosoplicatum Ĥrn. — Bajarunas 1910: 259 [non Ĥrnes, 1855]. Cerithium nodosoplicatum M. Hoern. — Schwetz 1912: 321 [non Ĥrnes, 1855]. Cerithium cf. nodosoplicatum M. Hoern. —Andrussov 1917: plate caption, pl. 15, fig. 24 [non Ĥrnes, 1855]. Cerithium nodoso-plicatum Ĥrn. — Zhizhchenko 1934: 64, pl. 9, fig. 21 [non Ĥrnes, 1855]. Cerithium cicur Zhizhchenko — Zhizhchenko 1934: 65, pl. 9, figs 18–19. Cerithium acriculus Zhizhchenko — Zhizhchenko 1934: 66, pl. 9, fig. 20. Potamides cicur Zhizhchenko — Zhizhchenko 1936: 202, pl. 21, figs 1–5. Bittium deforme Eichw. — Zhizhchenko 1936: pl. 20, figs 13–14 [non Eichwald, 1830]. Potamides acriculus Zhizhchenko — Zhizhchenko 1936: 207, pl. 20, figs 29–30. Potamides nodosoplicatus M. Ĥrnes — Zhizhchenko 1936: 205, pl. 21, figs 12–15, 17 [non Ĥrnes, 1855]. Potamides biseriatus Friedberg — Zhizhchenko 1936: 204, pl. 20, figs 23–28 [non Friedberg, 1914]. Potamides cicur Zhizhchenko — Zhizhchenko 1959: 250, pl. 16, figs 13–17. Potamides biseriatus Friedberg — Zhizhchenko 1959: 251, pl. 16, figs 18–22 [non Friedberg, 1914]. Potamides cicur Zhizhchenko, 1934 — Zelinskaya et al. 1968: 157, pl. 38, figs 3–4. Potamides (Pirenella) cicur ( Zhizhchenko, 1934) — Iljina 1993: 73, pl. 9, figs 4–9.? Potamides (Pirenella) gamlitzensis (Hilb.) — Goncharova & Iljina 1997: 69, unnumbered plate, fig. 30 [non Hilber, 1879].? Potamides (Pirenella) nodosoplicatus (M. Hoern.) — Goncharova & Iljina 1997: 69, unnumbered plate, fig. 31 [non Ĥrnes,

1855]. Potamides cicur (Zhizhchenko) — Guzhov 2015: 84. P [otamides]. cicur (Zhizhchenko) — Guzhov 2017: 26. P [otamides]. acriculus (Zhizhchenko) — Guzhov 2017: 26.

Type material. Holotype, TSNIGR No. 154/11330 (42169), SL: 9.2 mm, MD: 4.3 mm, designated by Zhizhchenko (1936: 202), illustrated in Zhizhchenko (1936: pl. 21, fig. 5), Figs 13A 1 –A 2. Paratype, TSNIGR No. 153/11330 (42169), SL: 10.5 mm, MD: 4.5 mm, illustrated in Zhizhchenko (1936: pl. 21, fig. 5). Paratype, TSNIGR No. 152/11330 (42168), illustrated in Zhizhchenko (1936: pl. 21, fig. 1).

Type locality. Mount Bryk, Cape Tarkhan ( Russia). Zhizhchenko (1934) mentioned the Roshnya and Elistanzhi rivers (Chechnya, Russia) as localities but said, that the illustrated shells come from Mount Bryk. In 1936 he wrote that the holotype was collected at the village Sultan (= Mount Bryk ) .

Stratigraphy. Middle Miocene, early Chokrakian.

Illustrated material. PIN 5872/16, SL: 11.2, MD: 4.2 mm, Belaya River ( Russia, Adygea), early Chokrakian, Figs 13B 1 –B 2. PIN 5872/17, SL: 9.5 mm, MD: 3.8 mm, Belaya River ( Russia, Adygea), early Chokrakian, Figs 13C 1 –C 2. PIN 5872/19, SL: 9.0 mm, MD: 3.7 mm, Belaya River ( Russia, Adygea), early Chokrakian, Figs 13D 1 –D 2. PIN 5872/18, SL: 10.0 mm, MD: 5.1 mm, Belaya River ( Russia, Adygea), early Chokrakian, Fig. 13E. PIN 5872/20, SL: 11.4 mm, MD: 4.2 mm, Mount Bryk ( Russia, Stavropol Krai), early Chokrakian, Fig. 13F. PIN 5872/21, SL: 11.6 mm, MD: 3.8 mm, Mount Bryk ( Russia, Stavropol Krai), early Chokrakian, Figs 13G 1 –G 2. Nr. TSNIGR 161/11330, Benoi ( Russia, Chechnya), early Chokrakian, TSNIGR Museum, St. Petersburg; holotype of Cerithium acriculus Zhizhchenko, 1934 , Fig 13H. NHM TG 27311, lectotype (designated herein) of Cerithium truncatum Baily, 1858 , Mramornaya gully (= “Gorge of Iphigenia”) ( Russia, Crimea) (see discussion on locality in nomenclator), early Chokrakian, Fig. 13I. PIN 5872/6, SL: 3.2, MD: 1.9 mm, Malyi Kamyshlak ( Russia, Crimea), early Chokrakian, Fig. 13 J. PIN 5872/7, SL: 3.55, MD: 1.7 mm, Mount Bryk ( Russia, Stavropol Krai), early Chokrakian, Fig. 13K.

Revised description. Small (10–14 mm), stout to elongate conical of 8–9 teleoconch whorls, with cyrtoconoid spire; apical angle ~35–40°. Protoconch conical of two smooth, convex whorls. Early teleoconch whorls with two closely spaced spiral cords placed mid-whorl. Third spiral cord appears around fourth teleoconch whorl above primary cords and quickly attains same strength. Cords become band-like after fourth teleoconch whorl and divide profile into three equal parts. Wide-spaced beads (10–12 on penultimate whorl) on spiral cords, strictly axially arranged without forming axial ribs. On mid-whorls, middle spiral cord weakens and narrows, leaving two strongly and coarsely beaded adsutural cords, separated by narrower weak central cord that in some specimens disappears completely. Last whorl slightly angulated at periphery; base rapidly contracting with two prominent peribasal spiral cords and narrow fasciole. No varices. Aperture wide, quadrate ovoid. Columella concave, smooth. Inner lip forming rim, well separated from base by narrow chink. Anal sinus narrowly incised. Outer lip slightly expanded, not thickened, with weak central angulation. Siphonal canal short, relatively narrow, incised, slightly deflected to the left.

Synonyms. The holotype of Cerithium acriculus Zhizhchenko, 1934 is a corroded specimen with untypical morphology (with two narrow spiral cords between the adsutural cords), which seems to resemble the morphs of Theodisca cicur with reduced sculpture. The morphs dominate in the Chokrakian from the Mount Bryk area. Acriculus -like specimens form transitions to normally sculptured T. cicur in the lower part of the Chokrakian section of Bryk and might present a local ecomorph of T. cicur .

Cerithium truncatum Baily, 1858 is based on two fragmentary specimens of which the better preserved one seems to represent a specimen of Theodisca cicur with cylindrical whorls, weakly developed beads and central spiral cord. This name would have priority but is variously preoccupied by Gray in Griffith & Pidgeon (1833) and Griffith & Pidgeon (1834).

Discussion. This species is reminiscent of the Badenian Theodisca theodisca ( Rolle, 1856) in the Central Paratethys and a phylogenetic relation between both coeval species is likely. Theodisca cicur differs from T. theodisca in its smaller size, stout outline and the lower number of teleoconch whorls. Early teleoconch whorls of T. theodisca are strongly angulated due to the dominant adapical spiral row of beads, whereas T. cicur lacks such prominent angulation. The latter feature allows a separation from the Sarmatian Theodisca biseriata ( Friedberg, 1914) .

P.cicur comprises several morphotypes, which might represent ecophenotypes. Shells from the zone of bioherms typically have two beaded spiral cords, whereas the central cord appears only on early whorls. This cord is poorly developed and reduced during subsequent shell growth. Shells from nearshore zone with inconstant salinity have commonly a narrow and poorly developed middle cord persisting up to the adult stage. Finally, shells from the sandy facies of Mount Bryk, deposited under reduced salinity, develop a somewhat more prominent central cord. These shells form also transitions to the acriculus- morph with reduced sculpture.

Distribution. Theodisca cicur was endemic to the Eastern Paratethys Sea during the early Chokrakian, being documented from the Crimea, Ciscaucasia and Transcaucasia .

Eastern Paratethys. Early Chokrakian (Middle Miocene): Crimea: Lake Chokrak, Malyi Kamyshlak, Cape Tarkhan, Yuzmak, Cape Zyuk; Ciscaucasia: Belaya River (= Tul'skii), Fars River, ravine Semikolennaya (Adygea), Novo-Kuvinsk (Karachai-Cherkessia), Mount Bryk (= Sultan, Sultanskoe), Kazinka, Podgornoe (Stavropol Krai, Russia) ( Iljina 1993; own data); Benoi, Elistanzhi River, Roshnya River (Chechnya, Russia) ( Zhizhchenko 1936); Transcaucasia: Tkvarcheli (= Kvezani) (Abkhazia), Dzhgali ( Georgia) ( Iljina 1993).