Andrusovia cyrensis, Anistratenko & Neubauer & Anistratenko & Kijashko & Wesselingh, 2021

Anistratenko, Vitaliy V., Neubauer, Thomas A., Anistratenko, Olga Yu., Kijashko, Pavel V. & Wesselingh, Frank P., 2021, A revision of the Pontocaspian gastropods of the subfamily Caspiinae (Caenogastropoda: Hydrobiidae), Zootaxa 4933 (2), pp. 151-197 : 163-165

† Andrusovia cyrensis sp. nov.

Fig. 5

urn:lsid:zoobank.org:act:3A413153-1A98-47A7-A93A-B00CC7CE8E04

Type material. Holotype: RGM 1310292 : 0.83 x 0.90 mm ( Fig. 5a, j, k, r ) . Paratypes: RGM 1310293 : 0.93 x 0.99 mm ( Fig. 5b, m ) ; RGM 1310294 : 0.81 x 0.89 mm ( Fig. 5c, d, l, q, s ) ; RGM 1310295 : 0.75 x 0.81 mm ( Fig. 5e, f, i, p, t ) .

Type locality. South Caspian Basin off Kura delta, Azerbaijan (locality 25f, sample 14-1); GPS coordinates: 39°17’13.14”N, 49°36’7.62”E ( WGS84 ) .

Age. Subfossil, late Holocene ( Hoogendoorn et al. 2005).

Other material. Three specimens from localities 25d and 25f ( RGM 1310296–1310298).

Etymology. From Cyrus, the Latin name of the Kura River.

Diagnosis. Low trochiform, conical, small Andrusovia with up to three convex, slightly stepped whorls, wide umbilicus, broadly ovoid aperture, weakly sinuate and weakly thickened peristome, strongly wrinkled protoconch with faint spiral threads and teleoconch microsculpture consisting of fine, densely spaced, slightly irregular, raised spiral threads, which are typically dissected into elongate beads.

Description. Small shell, slightly broader as high, with up to three whorls with stepped appearance. Protoconch low domical, cap-like, consisting of 1 whorl that measures c. 290–305 µm; protoconch covered with densely malleate sculpture that may become wider meshed and spikier on second half; faint traces of up to four spiral threads appear on first half near lower suture in some specimens; final triangular portion reaching from lower suture to end of protoconch, starting at c. 0.75 whorls, devoid of malleate sculpture but bearing growth rims that increase in strength towards transition to teleoconch; transition marked by growth stop and onset of fine prosocyrt growth lines. Teleoconch whorls covered with dense microsculpture consisting of fine, densely spaced, slightly irregular, raised spiral threads, which are typically dissected into elongate beads. Suture incised and deep. Body whorl attains c. 80% of total shell height, forms shallow base. Aperture wide, ovoid, with weak notch at contact to penultimate whorl; umbilicus circular, wide, deep. Peristome slightly thickened, sinuate.

Remarks. The new species resembles A. dybowskii superficially concerning the low trochiform shape, but it is distinctly smaller, has a lower spire, a smaller protoconch (290–305 µm versus 380–415 µm) at approximately the same number of whorls, more convex whorls and a teleoconch microsculpture that is so far unknown in any other Andrusovia species. Only specimens formerly attributed to Andrusovia andrusovi (here considered a synonym of A. dybowskii ; see above) more closely match A. cyrensis sp. nov. in terms of the depressed shell, but we consider the larger size, larger protoconch, more thickened shell and (apparent) lack of teleoconch microsculpture ( Fig. 2 ae), 3c, h) sufficient to distinguish them on the species level. The Pleistocene Andrusovia antecessor sp. nov. is even larger and has a higher spire with more whorls.

Distribution. Caspian Sea. So far only known from the late Holocene of the Kura delta deposits (South Caspian Basin).

Figures

FIGURE 2. Andrusovia dybowskii Brusina in Westerlund, 1903. (a, b, e) Lectotype, locality 26 (CNHM ZMKJ 50). (c, d, f) Paralectotype, locality 26 (CNHM ZMKJ 51). (g, h) Paratype of A. brusinai, locality 22 (MSU Lc-24598). (i–k) Specimen from Baer collection, locality 26 (ZB-M W.Dyb. 70). (l, m, q) Specimen from Baer collection, locality 26 (ZB-M W.Dyb. 28). (n–p) Specimen from Baer collection, locality 26 (ZB-M W.Dyb. 28). (r, v, w) Specimen from Baer collection, locality 26 (ZB-M W.Dyb. 116). (s–u) Specimen from Baer collection, locality 26 (ZB-M W.Dyb. 70). (x) Specimen from Baer collection, locality 26 (ZB-M W.Dyb. 70). (y) Paratype of H. marina, locality 22 (MSU Lc-24614c). (z, ad) Paratype of H. marina, locality 22 (MSU Lc-24614a). (aa) Paratype of H. marina, locality 22 (MSU Lc-24614b). (ab) Specimen from Baer collection, locality 26 (ZB-M W.Dyb. 70). (ac) Specimen from Baer collection, locality 26 (ZB-M W.Dyb. 28). (ae) Paratype of A. andrusovi, locality 18 (MSU Lc-24601). Scale bar = 1 mm.

FIGURE 5. Andrusovia cyrensis sp. nov. from the late Holocene of the South Caspian Sea off the Kura delta, Azerbaijan. (a, j, k, r) Holotype, locality 25f (RGM 1310292). (b, m) Paratype, locality 25d (RGM 1310293). (c, d, l, q, s) Paratype, locality 25f (RGM 1310294). (e, f, i, p, t) Paratype, locality 25f (RGM 1310295). (g) Specimen from locality 25d (RGM 1310296). (h, n) Specimen from locality 25f (RGM 1310297). (o) Specimen from locality 25f (RGM 1310298). Scale bars = 500 µm (a–h), 100 µm (i, j, l–q, s, t), 50 µm (k), 10 µm (r).