Bellardithala obsoleta
Creators: name: Sacchetti, Claudia
name: Landau, Bernard
name: Ávila, Sérgio P.
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Gastropoda
Neogastropoda
Costellariidae
Bellardithala
Bellardithala obsoleta

description: Bellardithala obsoleta (Brocchi, 1814)
Plate 5 H 1 -H 2
* Voluta obsoleta Brocchi 1814: 646, pl. 15, fig. 30.
Mitra striata Eichwald 1830: 221.
Mitra obsoleta Brocch. — Bellardi 1850: 28, pl. 2, fig. 29.
Mitra obsoleta Brocchi —Fontannes 1880: 87, pl. 6, fig. 9.
Micromitra pusilla Bellardi 1888: 8, pl. 6, fig. 48.
Micromitra obsoleta (Brocch.) — Bellardi 1888: 9, pl. 6, fig. 49.
Micromitra mangeliaeformis Bellardi 1888: 9, pl. 6, fig. 50.
Thala obsoleta var. elatocostata Sacco 1904: 88, pl. 19, fig. 24.
Thala obsoleta var. angustolonga Sacco 1904: 88, pl. 19, fig. 25.
Pusia (Pusia) (Pusia) obsoleta (Brocchi, 1814) —Rossi Ronchetti 1955: 243, fig. 129.
Voluta obsoleta Brocchi, 1814 — Pinna & Spezia 1978: 169, pl. 68, fig. 2.
Micromitra mangeliaeformis Bellardi, 1888 — Ferrero Mortara et al. 1981: 172, pl. 54, fig. 3.
Micromitra pusilla Bellardi, 1888 — Ferrero Mortara et al. 1981: 172, pl. 54, fig. 6.
Thala obsoleta (Brocchi, 1814) — Giannuzzi-Savelli & Reina 1983: 233, text-fig. 2.
Thala obsoleta (Brocchi, 1814) — Davoli 2000: 210, pl. 7, fig. 10, pl. 8, figs. 1, 2.
Thala obsoleta (Brocchi, 1814) — Chirli 2002: 56, pl. 28, figs. 5-12.
Thala obsoleta (Brocchi, 1814) — Landau et al. 2011: 29, pl. 15, fig. 6.
Thala obsoleta (Brocchi, 1814) — Landau et al. 2013: 218, pl. 34, fig. 18-19.
non Mitra obsoleta Bronn [sic]—Hörnes 1852: 110, pl.10, fig. 32. [= Bellardithala kovaci Harzhauser & Landau, 2021).
non Thala obsoleta (Brocchi, 1814) — Bałuk 1997: 39, pl. 11, fig. 2 [= Bellardithala kovaci Harzhauser & Landau, 2021).
Santa Maria material examined. Maximum height 5.9 mm, width 2.0 mm. DBUA-F 542-4 (1), Ponta dos Frades, Santa Maria Island, Azores, Touril Complex, Lower Pliocene.
Description. Shell medium-sized, moderately slender fusiform with cyrtoconoid spire and narrowly incised suture. Protoconch not preserved. Teleoconch of four weakly convex whorls, with periphery at abapical suture, rapidly increasing in height. First teleoconch whorl with rounded axial ribs, crossed by spiral threads (specimen too worn to count cords). Regularly spaced predominant axial ribs crossed by about six or seven spiral cords on penultimate whorl. Last whorl almost straight sided (incomplete, missing siphonal part), hardly constricted at base, bearing narrow cords and broader ribs, too worn to count, adapical subsutural spiral cord most prominent. Cords over fasciole prominent. Aperture moderately narrow with shallow anal sinus. Columellar callus indistinct, poorly delimited. Columella with three prominent folds (incomplete). Outer lip thickened, denticulate within. Siphonal canal missing.
Discussion. The genus Thala H. & A. Adams, 1853 has been used by authors for European Neogene species with a wide range of morphologies, none of which truly represents the genus Thala (Harzhauser & Landau 2021). Voluta obsoleta Brocchi, 1814, was placed in a new genus Bellardithala Harzhauser & Landau, 2021, characterised by medium-sized Thala - and Mitromica - like species with moderately slender fusiform shells, cancellate, weakly beaded or strongly reduced sculpture. Differing from Mitromica Berry, 1958, in their episodic growth, indicated by the formation of denticles in juvenile specimens and from Thala in the predominant axial sculpture on early spire whorls. Occasionally with elongate denticles within outer lip.
The single Azorean specimen is incomplete and worn. Compared to specimens from the Mediterranean Pliocene the spiral cords are relatively fewer and stronger. However, there is some variability in the sculpture, and we provisionally consider them conspecific.
Distribution. Middle Miocene: Proto-Mediterranean Sea (Serravallian), Karaman Basin, Turkey (Landau et al. 2013). Upper Miocene: Proto-Mediterranean Sea (Tortonian), Po Basin, Italy (Bellardi 1888; Davoli 2000). Lower Pliocene: Atlantic, Santa Maria Island, Azores, Guadalquivir Basin, Spain (Landau et al. 2011), northeastern Spain (NHMW coll.), Roussillon Basin, France (Fontannes 1880); central Mediterranean, Italy (Bellardi 1888; Chirli 2002). Upper Pliocene: western Mediterranean, Estepona Basin, Spain (NHMW coll.).
description: Published as part of Sacchetti, Claudia, Landau, Bernard & Ávila, Sérgio P., 2023, The Lower Pliocene marine gastropods of Santa Maria Island, Azores: Taxonomy and palaeobiogeographic implications, pp. 1-150 in Zootaxa 5295 (1) on pages 77-78, DOI: 10.11646/zootaxa.5295.1.1, http://zenodo.org/record/7965273