Fedosovia, Harzhauser & Landau, 2021

Harzhauser, Mathias & Landau, Bernard, 2021, An overlooked diversity-the Costellariidae (Gastropoda: Neogastropoda) of the Miocene Paratethys Sea, Zootaxa 4982 (1), pp. 1-70 : 34

Genus Fedosovia nov. gen.

Type species. Mitra (Callithea) fuchsi Hoernes & Auinger, 1880 , middle Miocene , Paratethys Sea, Romania .

Diagnosis. Large, moderately broad fusiform shell, with beaded sculpture, differing from Thala in the development of a parietal denticle and the less cyrtoconoid spire. Protoconch paucispiral, of weakly convex, smooth whorl. Teleoconch whorls with dense pattern of axial ribs and spiral cords forming densely spaced ‘pillow-like’, subquadrate nodes at intersections. Axial ribs of early teleoconch whorls of type species bearing three spiral rows of nodes with tiny spines on middle spiral row [not preserved in F. zibinica ]. Aperture moderately narrow to wide, with three columellar folds; adapical two folds very prominent. Columellar callus narrow, abapically contracting, no lirae inside aperture. Siphonal canal moderately long, straight or slightly bent to left. No signs of episodic growth.

Description. As for type species.

Etymology. In honour of Alexander Fedosov (Russian Academy of Sciences, Moscow), in gratitude for the discussions on Paratethyan Costellariidae .

Included species. Mitra (Callithea) fuchsi Hoernes & Auinger, 1880 , middle Miocene, Romania; Mitra zibinica Toldo, 1889 , late Miocene, Italy.

Stratigraphic and geographic range. Middle Miocene (Badenian) deposits of the Central Paratethys Sea and late Miocene of the proto-Mediterranean Sea.

Palaeoenvironment. Unknown; most probably from middle neritic depositional environments with pelitic bottom (based on sediment from the aperture).

Discussion. Fedosovia differs from other costellariid genera by the combination of a peculiar ‘pillow-like’ sculpture and a paucispiral protoconch (as opposed to Ebenomitra , which has a paucispiral protoconch, but lacks the peculiar sculpture). Protoconch of paucispiral or multispiral type is not a useful distinguishing character in many gastropod groups. However, amongst the Costellariidae, Fedosov et al. (2017) placed importance at supraspecific level to protoconch type in many of their genera, and specified the protoconch type in his generic descriptions. We follow this lead here and consider the protoconch type a genus-specific character in Fedosovia .

The paucispiral protoconch excludes a relation with Vexillum , although the extant Vexillum piceum ( Pease, 1860) , from Réunion and Hawaii, develops a comparable sculpture (but is much smaller, SH <10 mm). A paucispiral protoconch occurs in the extant Atlantilux Huang, 2015 but Atlantilux species are characterised by a wide, slightly concave subsutural ramp and convex periphery close to the abapical suture. Atlantilux is also distinguished from Fedosovia by the sculpture of dense axial riblets in the subsutural area opposed by wide fold-like axial ribs along the periphery (see Fedosov et al., 2017). Fedosovia is superficially reminiscent of Costapex Fedosov, Herrmann & Bouchet, 2017 in shape and sculpture. A closer relationship with this extant genus, however, is unlikely in respect to the paucispiral protoconch and the presence of only three columellar folds instead of four.