Grovesella nevadensis, Davydov, 2011

Davydov, Vladimir I., 2011, Taxonomy, nomenclature, and evolution of the early schubertellid fusulinids, Acta Palaeontologica Polonica 56 (1), pp. 181-194 : 188

Grovesella nevadensis sp. nov.

Fig. 2J–T.

Etymology: After the state Nevada ( USA) where numerous specimens of the species were recovered.

Type material: Holotype: SUI 114224 ( Fig. 2Q), axial section; paratypes: SUI 114217 ( Fig. 2J), axial section; SUI 114218 ( Fig. 2K), axial section; SUI 114219 ( Fig. 2 LJ), axial section; SUI 114220 ( Fig. 2M), axial section; SUI 114221 ( Fig. 2N), axial section; SUI 114222 ( Fig. 2O), axial section; SUI 114223 ( Fig. 2P), axial section; SUI 114225 ( Fig. 2R), axial section; SUI 114226 ( Fig. 2S), axial section; SUI 114227 ( Fig. 2T), axial section.

Type locality: Arrow Canyon section, Bird Spring Formation, Nevada, USA .

Type horizon: Eoparafusulina linearis beds, late Artinskian, Cisuralian.

Diagnosis.—Miniature test with nautiloid and broadely rounded periphery and nearly planispiral coiling, poorly visiable but most probably two−layered wall; it is lacking chomata.

Description.—Test is very small, with 2–2.5 volutions, nautiloid with broadly rounded periphery and flat to mildly umbilicate flanks. Coiling is planispiral or nearly planispiral. The axis of initial volution in some specimens sometimes is at a small angle in respect of second volution.

Length of the test is 160–200 µm, diameter (width) 180–250 µm, with form ratio of 0.79–0.9. Outer diameter of proloculus is 25–60 µm. Wall thin, poorly visible, sometimes two−layers, a darker, thin tectum and slightly lighter, structureless lower tectorium can be observed. Thickness of the wall in the final volution is 3–10 µm. Chomata generally absent, but sometimes dark secondary deposits present on the chamber floor in the final volution ( Fig. 2O). Because of lack of chomata, nether shape or size of the tunnel could be determined.

Remarks.—The species described here closely resembles Grovesella staffelloides ( Suleimanov, 1949) from the late Asselian and Sakmarian of southern Urals but differs from it in smaller size of the test and the initial chamber, a smaller form ratio and lack of chomata. From Grovesella tabasensis Davydov and Arefifard, 2007 it differs in having a wider test and consequently a greater form ratio.

Stratigraphic and geographic range.—Moscovian, Pennsylvanian through Artinskian, Cisuralian in Nevada and Donets Basin.