Acicula telum Páll-Gergely, 2023

Páll-Gergely, Barna, Mumladze, Levan, Grego, Jozef & Giokas, Sinos, 2023, The genus Acicula W. Hartmann, 1821 in the Caucasus (Gastropoda: Caenogastropoda: Aciculidae), Zootaxa 5239 (4), pp. 451-476 : 463-466

Acicula telum Páll-Gergely , n. sp.

( Figs. 9 , 10 )

Acicula moussoni — Boeters et al. 1989: 72, fig. 72 (partim)

Type material. Holotype: RUSSIA, Western Caucasus , vicinity of Sochi , valley of the Khosta river , at Rassvet village, flotsam of Khosta, 43°32.856′N, 39°52.892′E, leg. L. Németh, 20 June 1988, H = 2.36 mm, D = 0.93 mm ( SMF 366182 ) . Paratypes: RUSSIA, same data as for holotype, 46 adult shells ( LN 10681 ) ; Western Caucasus, valley of River Mzimta towards Krasnaya Polyana , 26/33. km, in the "gorge" (approximate GPS coordinates: 43°31.267′N, 39°59.903′E), leg. L. Németh, 18 June 1988, 1 adult shell ( LN 10564 ) ; Western Caucasus, West Dagomisi River, vicinity of Nor Luis village , ca. 10 km (approximate GPS coordinates: 43°42.713′N, 39°40.003′E), river debris, leg. L. Németh, 19 June 1988, 5 shells ( LN 10697 ) . GEORGIA, Tskhenistskali valley after Tsageri , between iron and stone bridge (approximate GPS coordinates: 42°39.411′N, 42°46.280′E), leg. L. Németh, 11 June 1988, 5 shells ( LN 10357 ) ; Abkhazia, Novij Afon , above the tunnel near the railway station, 43°5.518′N, 40°48.938′E, leg. L. Németh, 16 June 1988, 10 shells ( LN 10523 ) .

Additional material examined. RUSSIA, s ame data as for holotype, LN 10681/ 91 juvenile /broken shells; Western Caucasus , valley of River Mzimta towards Krasnaya Polyana , 26/37. km (from Aldler), side stream valley (approximate GPS coordinates: 43°38.001′N, 40°5.062′E), leg. L. Németh, 18 June 1988, 1 subadult shell (identification questionable) ( LN 10571 ); Western Caucasus, valley of River Mzimta towards Krasnaya Polyana, 26/33. km, in the "gorge" (approximate GPS coordinates: 43°31.267′N, 39°59.903′E), leg. L. Németh, 18 June 1988, 3 broken shells (identification questionable) ( LN 10564 ) .

Diagnosis. Among Caucasian Acicula , A. telum n. sp. is uniquely characterized by the bullet shaped, relatively wide shell (D/H ratio: 0.37–0.45, average: 0.42), an aperture profile that is parallel to the shell axis or slightly opisthocline, and the acutely angled parieto-palatal apertural transition.

Description. Shell small, bullet- or torpedo-shaped with blunt apex, sides curved, shell widest at its base, whorls slightly bulging. Body whorl rounded, and its periphery rounded to somewhat flat-sided from basal direction (visible in standard apertural view). Fresh shells glossy, yellowish to dark brown or reddish, sutural ridge clearly visible, starting from beginning of teleoconch, at first does not differ from shell colour, but gradually becomes darker, on last 2–3 whorls slightly darker than basic shell colour. Apex smooth, boundary of protoconch and teleoconch hardly visible, whorls with irregularly arranged, dense longitudinal furrows, penultimate whorl above aperture with 8–14 furrows in apertural view (variable between samples), grooves in most cases abruptly become denser on ca. last quarter whorl. Whorls 4.5–6, body whorl occupies (i.e., H/BWH) ca. 46–54 % of the total height. Aperture parallel with the shell axis or very slightly opisthocline, aperture profile nearly straight or slightly curved. Neck bulge absent. Aperture teardrop-shaped, parieto-palatal angle conspicuously pointed, peristome slightly thickened, its basal and columellar side reflected, partly covers periomphalum. Parietal callus present but weak even in mature shells, transparent and matte in fresh shells, white in corroded shells. Angularis absent. Umbilical area densely grooved due to the increased density of grooves on the last quarter whorl.

Number of grooves on last whorl. 7–16, average: 11.16 (SD=+/-2.5) (n = 19).

Measurements (in mm). H = 1.89–2.41, average: 2.17 (SD=+/-0.18); D = 0.78–1.02, average: 0.91 (SD=+/- 0.7); D/H: 0.37–0.45, average: 0.42 (SD=+/-0.02) (n = 16).

Intraspecific variability. The available populations of this new species show some variability in terms of shell size and groove density (see Table 1 ).

Differential diagnosis. Acicula telum n. sp. is readily distinguishable from other Caucasian congeners due to its widely-based, bullet-shaped shell. Furthermore, the aperture profile of this species is straight, parallel to the shell axis or slightly opisthocline in lateral view, whereas it is prosocline in A. moussoni and A. parcelineata . Lastly, the aperture of A. telum n. sp. shape is also somewhat different from that of the other two species. Namely, the parietal and palatal walls meet under a smaller angle resulting in a more pointed upper part of the aperture.

Etymology. The specific epithet (bullet in Latin) refers to the shell shape of the new species. It is a noun in apposition.

Distribution. Acicula telum n. sp. is known from the northern part of the Caucasus Mountains ( Fig. 7 ).

Remarks. This species is clearly different from the other large Caucasian species ( A. moussoni ) due to the stable, diagnostic shell characters, and the fact that A. moussoni and A. telum n. sp. were collected syntopically at two sites.

Figures

FIGURE 7. Distribution of Acicula species in the Caucasus Mts. The symbols marked with numbers (1: Surami range, 2: Manglisi, 3: Martkopi, 4: North Ossetia) do not represent georeferenced localities for Acicula moussoni O. Boettger, 1879 and Acicula parcelineata (Clessin, 1911).

FIGURE 9. Acicula telum Páll-Gergely, n. sp. A: Greater Caucasus Mts, 13 km north-northeast from Sochi; (RMNH; REM- Foto: J.H.W. Krom); B: holotype (LN 10681, specimen1, SMF 366182); C: LN 10564, specimen1; D: LN 10697, specimen1; E: ex. LN 10357, specimen1; F: LN 10523, specimen1. Photos: B. Páll-Gergely except for A (images taken from Boettger et al. 1989).

FIGURE 10. Synoptic view of Caucasian Acicula. Upper left shell: Acicula limbata Reuss, 1861; other shells in the upper two rows: Acicula moussoni O. Boettger, 1879, third row: Acicula telum Páll-Gergely, n. sp., fourth row: Acicula parcelineata (Clessin, 1911).