Betaneospirifer stepanovi Poletaev, 2018

Poletaev, Vladyslav, 2024, New and revised taxa of Carboniferous spiriferides (Brachiopoda, Spiriferida) from the Donets Basin (Ukraine) and South Urals (Russia), European Journal of Taxonomy 968, pp. 132-155 : 142-143

Betaneospirifer stepanovi Poletaev, 2018

Fig. 5A–C

Betaneospirifer stepanovi Poletaev, 2017: 74 (nom. nud.).

Betaneospirifer stepanovi Poletaev, 2018: 84 , pl. 110 figs 3–5.

Spirifer (Spirifer) fasciger var. sterlitamakensis – Stepanov 1948: 41, pl. 7 fig. 12.

Neospirifer sterlitamakensis – Mironova 1967: 43, pl. 4 fig. 6. — Lapina 1975: 191, pl. 85 fig. 2. — Alexandrov & Einor 1979: 75, pl. 28 fig. 18.

Diagnosis

Small shells with transverse outline; hing line short; cardinal extremities rounded or orthogonal; three to four folds on each side of ventral valve; ribs relatively few, narrow, forming fascicles.

Material examined

Holotype (fig. 5A) RUSSIA • Bashkortostan, Belaya River, Tabynskoie village, Voskresenka Mountain ; Gzhelian ; Mironova 1967 Coll.; CNIGR Museum 8491.48 .

Paratypes RUSSIA • 1 spec.; Urals, Bashkortostan, Belaya River, Tabynskoie village , Voskresenka Mountain ; Gzhelian; Stepanov 1948 Coll.; VNIGRI Museum 163 • 5 specs; Bashkortostan, Zilim River, Tash-Asty village ; upper Moscovian; Alexandrov and Einor 1979 Coll.; GMNTSU 79.226 (fig. 5B) .

Description

Shell small to medium in size (15–30 mm in width), transversely oval in outline; hinge line slightly shorter than greatest width. Ventral valve evenly convex with a well-delineated umbo; has three to four longitudinal plicae on each side. Apex beak-shaped, curved above the hinge line. Ventral interarea triangular, apsaclin. Cardinal extremities small, obtuse or rounded. Sulcus deep, sharply expressed, pointed, forming a small tongue at the anterior margin, three ribs on each slope of sinus and one along axis. On the sides narrow simple radial ribs, collected in four bundles of three ribs each, separated by sharp intervals. The outer peculiarities of the dorsal valve (main axial fold and four folds on each side) are well visible on the well safed paratype of the species. Inner structure of the shell is few investigated. Ventral valve has a pair of long thin dental plate.

Remarks

Betaneospirifer stepanovi differs from B. sterlitamakensis (Gerasivov, 1929) by its suboval shell, much shorter hinge margin, rounded cardinal extremities, and by the essential difference in stratigraphic distribution. The stratigraphic range of B. stepanovi includes the late Pennsylvanian, but the range of B. sterlitamakensis is Early Permian (Asselian and early Sakmarian). The specimens examined differ greatly from the other species of Betaneospirifer in their small size as well as geographic and stratigraphic distributions. It is likely that the studied specimens represent the oldest (Late Pennsylvanian) species of the genus Betaneospirifer .

Stratigraphic and geographic range

Late Moscovian and Late Pennsylvanian; South Urals, Russia.

Figures

Fig. 5. Betaneospirifer stepanovi Poletaev, 2018 from Bashkortostan (Urals, Russia). A. Holotype CNIGR 8491/48 (Mironova 1967 Coll.) from Tabynskoie; ventral view (copy from Mironova 1967: pl. 4 fig. 6). B. Paratype GMNTSU 79/226 (Alexandrov & Einor 1979 Coll.) from Tash-Asty; ventral and dorsal views (copy from Alexandrov & Einor 1979: pl. 28 fig. 18). C. Paratype VNIGRI 163 (Stepanov 1948 Coll.) from Tabynskoie village; ventral and dorsal views (copy from Stepanov 1948: pl. 7 fig. 12). Scale bar units = 1 mm.