Bellardithala kostejana Harzhauser & Landau 2021, nov. comb.
Creators: name: Harzhauser, Mathias
name: Landau, Bernard
Publisher: name: Zenodo
Year: 2021
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Gastropoda
Neogastropoda
Costellariidae
Bellardithala
Bellardithala kostejana

description: Bellardithala kostejana (Boettger, 1906) nov. comb.
Figs 8D 1 –D 2, E 1 –E 2, F
* Mitra (Thala) partschi M. Hö. var. kostejana n.— Boettger 1906: 11.
Pusia (Thala) partschi kostejana (Boettger) — Zilch 1934: 285, pl. 17, fig. 13.
Thala partschi kostejana (Boettger, 1906) — Rosenberg & Salisbury 2003: 3.
Type material. Lectotype: SMF 360340 (= SMF XII.2214 a), SL: 5.7 mm, MD: 2.1 mm, designated and illustrated by Zilch (1934, pl. 17, fig. 13), Senckenberg Museum, Frankfurt/Main, Germany, Coşteiu de Sus (Romania), figs 8D 1 –D 2. Paralectotypes: 28 specimens, SMF XII 2214 b, Senckenberg Museum, Frankfurt / Main, Germany, Coşteiu de Sus (Romania).
Additional material. NHMW 2020 /0064/0001, SL: 5.8 mm, MD: 2.3 mm, Lăpugiu de Sus (Romania), figs 8E 1 –E 2; NHMW 2020 /0064/0002, SL: 5.5 mm, MD: 2.3 mm, Lăpugiu de Sus (Romania), fig. 8F.
Revised description. Shell small, moderately broad fusiform with conical to slightly cyrtoconoid spire. Protoconch poorly preserved, high conical with three regularly convex whorls. Teleoconch of 4.5 weakly convex to nearly straight-sided whorls with periphery at abapical suture, separated by incised suture.Axial sculpture of densely spaced, orthocline axial ribs, crossed by densely spaced spiral cords, forming delicate, spirally elongated pits in the interspaces. Spiral sculpture most prominent in axial interspaces, but strongly reduced on axial ribs. Last whorl moderately constricted at base. Aperture moderately narrow, with indistinct anal sinus. Columellar callus narrow. Columella with four columellar folds, weakening rapidly abapically. Outer lip weakly thickened, bearing about nine prominent denticles within. Siphonal canal moderately short, bent slightly left, with shallow siphonal notch.
Shell measurements and ratios. SL: 5.5–5.8 mm, MD: 2.1–2.3, mm, AA: 26–43°, SL/MD: 2.6–2.8, AL/AW: 3.4–5.0, AH/S: 2.4–2.6.
Discussion. Bellardithala kostejana (Boettger, 1906) can be separated from all its Paratethyan congeners in having a strongly oblique suture. It is superficially similar to B. partschi (Hörnes, 1852), which led Boettger (1906) to described it as variety of the latter. However, it differs in its broader, regularly conical spire, its less incised suture, its finer sculpture, comprising a higher number of axial ribs and spiral cords, and the absence of a prominent subsutural spiral cord, as well as more oblique suture. In addition, B. kostejana is constantly smaller. The occurrence of B. kostejana in offshore marls indicates also an environmental separation from B. partschi, which is restricted to near shore occurrences.
Hölzl (1973: 93) mentioned Thala cf. partschi (M. Hoernes) from the Ottnangian (middle Burdigalian) of Gernergraben in Bavaria (without illustration). This would be the oldest record for this group from the Paratethys Sea. We have not seen this specimen but the generally poor preservation of the material from Gernergraben usally does not allow unambiguous identifications.
Palaeoenvironment. The assemblages from Coşteiu de Sus suggests middle neritic palaeoenvironments with soft bottom (own data).
Distribution in Central Paratethys. Badenian (middle Miocene): Făget Basin: Coşteiu de Sus, Lăpugiu de Sus (Romania).
description: Published as part of Harzhauser, Mathias & Landau, Bernard, 2021, An overlooked diversity-the Costellariidae (Gastropoda: Neogastropoda) of the Miocene Paratethys Sea, pp. 1-70 in Zootaxa 4982 (1) on pages 24-25, DOI: 10.11646/zootaxa.4982.1.1, http://zenodo.org/record/4921842