Biwaella zhikalyaki, Davydov, 2011
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publication ID |
https://doi.org/ 10.4202/app.2010.0026 |
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persistent identifier |
https://treatment.plazi.org/id/7169E261-FFD2-FFC3-7424-F8158C19C280 |
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treatment provided by |
Felipe |
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scientific name |
Biwaella zhikalyaki |
| status |
sp. nov. |
Biwaella zhikalyaki View in CoL sp. nov.
Fig. 3A–L View Fig .
Etymology: The species named after the Director of Artemgeology, Ukraine, Dr. Nikolay Vasilievich Zhikalyak who supports my study in the Donets Basin.
Type material: Holotype: SUI 114229 View Materials ( Fig. 3C View Fig ), axial section; paratypes: SUI 114228 View Materials ( Fig. 3A View Fig ), axial section; SUI 114230 View Materials ( Fig. 3E View Fig ), axial section; SUI 114231 View Materials ( Fig. 3F View Fig ), axial section; SUI 114232 View Materials ( Fig. 3G View Fig ), axial section; SUI 114233 View Materials ( Fig. 3H View Fig ), axial section; SUI 114234 View Materials ( Fig. 3I View Fig ), axial section; SUI 114235 View Materials ( Fig. 3J View Fig ), axial section; SUI 114236 View Materials ( Fig. 3K View Fig ), axial section; SUI 114237 View Materials ( Fig. 3L View Fig ), axial section.
Type locality: Kalinovo section near Kalinovo village , Luganskaya County, western Donets Basin, Ukraine .
Type horizon: Limestone P 2, Darvasoschwagerina donbassica – Schagonella proimplexa beds, early Gzhelian, Pennsylvanian.
Diagnosis.—Large elongate−fusiform test with pointed polar ends, tight coiling initially and loose at maturity, wavy septae, small, but prominent chomata in all volutions and wide tunnel.
Description.—Large, elongate−fusiform test with roundly pointed polar ends possessing 5–6 volutions. First–second volutions are nearly globular. Starting from the third volution, test elongates quite rapidly and reaches elongate−fusiform outline in fourth and following volutions. Initially tight coiling becomes much looser starting from the fourth volution. The initial volution coiled with large to very small angle in respect to outer volutions. In some forms coiling is planispiral or nearly planispiral. Test with length of 1.4–1.96 mm and diameter 0.48–0.65 mm producing form ratio 2.6–3.1 in the final volution. Outer diameter of proloculus varies between 45 and 80 µm, but generally is around 50–60 µm. Wall thin initially (15–20 µm), gradually becomes very thick and reaches thickness 40–45 µm in final volution. It is two−layered with thin dark tectum and thick lighter lower tectorium. Wall in the final volution penetrated by coarse pores up to 7–8 µm in diameter. Pores can be observed also in the volution before the final, but not elsewhere. Septa are straight or slightly wavy throughout the length except at the polar ends where they are fluted. Chomata very small initially are not always present in the final volution. Tunnel low and narrow initially becomes quite wide in the final volution.
Remarks.—The described species somewhat resembles the undescribed Biwaella sp. No 1 from the late Asselian of Darvas, Central Asia ( Leven and Shcherbovich 1978: 87) and Sakmarian of Afghanistan ( Leven 1971), but differs in having a smaller more elongate test, and consequently greater form ratios, better developed chomata in the internal volutions, and in fluting of the septa in the polar ends.
Stratigraphic and geographic range.— Darvasoschwagerina donbassica – Schagonella proimplexa Zone , early Gzhelian, Pennsylvanian, Donets Basin.
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