Biwaella poletaevi, Davydov, 2011

Davydov, Vladimir I., 2011, Taxonomy, nomenclature, and evolution of the early schubertellid fusulinids, Acta Palaeontologica Polonica 56 (1), pp. 181-194 : 190-192

Biwaella poletaevi sp. nov.

Figs. 4A–H , 5A .

1978 Biwaella ex gr. omiensis ; Leven and Shcherbovich, 1978: 87, pl.

1: 15. 1978 Biwaella sp. No. 2; Leven and Scherbovich, 1978: 88, pl. 1: 16.

Etymology: In honor of my friend and great Donets geologist and paleontologist Vladislav Innokent’evich Poletaev.

Type material: Holotype: SUI 114241 ( Fig. 4E ), axial section; paratypes: SUI 114238 ( Fig. 4A ), axial section; SUI 114239 ( Fig. 4C ), axial section; SUI 114240 ( Fig. 4D ), axial section; SUI 114242 ( Fig. 4F ), axial section; SUI 114243 ( Fig. 4G ), axial section; SUI 114243 ( Fig. 4H ), 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−subcylindrica test with rounded polar ends, nearly unifome coiling, wavy septae, poorly developed chomata that are often absent in the final volution.

doi:10.4202/app.2010.0026

Eostaffellina

Description.—Large, subcylindrical test of 5–6 volutions with broadly rounded polar ends. Test elongates quite rapidly starting from the third volution and becomes subcylindrical in outline in the two outer volutions. The coiling is planispiral or nearly planispiral. Initial volution is coiled tight then expands uniformly but rapidly. The final volution is loosely coiled. Test with length of 2.0– 2.5 mm and diameter 0.57–0.65 mm producing form ratio 3.2–4.1 in the final volution. Outer diameter of proloculus is 40–60 µm. Wall is thin initially, reaching thickness up to 20–30 µm in the final volution. Its internal structure is the same as in Biwaella zhikalyaki sp. nov. Septa are straight or slightly wavy throughout the length except at the polar ends where they are fluted. Chomata in early volutions are prominent, but absent in two outer volutions. Tunnel is moderate in height and width throughout the growth.

Remarks.—This species strongly resembles Biwaella ex gr. omiensis Morikawa and Isomi and Biwaella sp. No. 2 from middle–late Asselian of Darvas, Tadzhikistan, Central Asia (Leven and Scherbovich 1978) in its subcylindrical outline in two outer volutions, weak septal fluting throughout the length of the test, intensive fluting in polar ends, and lack of chomata in the two outer volutions. Biwaella omiensis Morikawa and Isomi, 1960 possesses some similarities with the described species but the described species differs in its rather fusiform outline of the test, smaller size and much smaller chomata.

Stratigraphic and geographic range.— Schagonella proimplexa Zone , early Gzhelian, Pennsylvanian, Donets Basin; middle–late Asselian of Darvas, Central Asia.

Figures

Fig. 4. Type of Biwaella and Biwaella poletaevi sp. nov. A–H. Biwaella poletaevi sp. nov. A–G. Kalinovo section, P 2 Limestone, Donets Basin, Ukraine. 2 A. SUI 114238, sample A−3/31a−8, axial section of paratype (A1), box indicates the enlarged part of final volution in A1 showing coarse mural pores (A2). B. SUI 114239, sample A−3/31a−5, axial section of paratype. C. SUI 114240, sample A−3/31a−77; sagital section of paratype. D. SUI 114241, sample A−3/31a−83, axial section of holotype.E. SUI 114242, sample A−3/31a−84, axial section of paratype.F. SUI 114243, sample A−3/31a−96, axial section of paratype.G. SUI 114244, sample A−3/31a−8; sagital section of paratype. H. Biwaella omiensis Morikawa and Isomi, 1960, repository unknown, axial section of holotype, from Morikawa and Isomi (1960:pl. 54:1);?Artinskian; Minamitoba, near Lake Biwa, Shiga Prefecture, Japan.Scale bars:A1, D–F, H 1 mm, C 0.5 mm, A2 0.1 mm, G 0.1 mm.

Fig. 5. The types of porosity in keriothecal and non−keriothecal wall. All specimens from Kalinovo section, P 2 Limestone, lower Gzhelian, Donets Basin, 2 Ukraine. A. Biwaella poletaevi sp. nov., SUI 114245, axial section of paratype, sample A−3/31a−3. B. Biwaella sp., SUI 114246, oblique section, arrow points to coarse mural pores MP; the diameter of the pores is the same elsewhere within the wall; sample A−3/31a−86. C, D. Schubertella subkingi Putrja, 1939. C. SUI 114247, axial section, sample A−3/31a−9. D. SUI 114248, axial section, sample A−3/31a−73. E. Darvasoschwagerina archaica (Leven and Scherbovich, 1978), SUI 114249, axial section, sample A−3/31a−22. F. Darvasoschwagerina sp., SUI 114250, oblique section, arrows point to the two different types of pores: UK − fine pores in upper keriotheca, LK − coarse pores in lower keriotheca; sample A−3/31a−22. G. Darvasoschwagerina satoi (Ozawa, 1925), SUI 114251, axial section, sample A−3/31a−9. H–M. Nodosinelloides sp. H. SUI 114252, axial section, sample A−3/31a−16. I. SUI 114253, axial section, sample A−3/31a−84. J. SUI 114254, axial section, sample A−3/31a−4. K. SUI 114255, axial section, sample A−3/31a−5. L. SUI 114256, axial section, sample A−3/31a−5. M. SUI 114257, axial section, sample A−3/31a−104. Scale bars A, B, E, G 1 mm, C, D, F 0.5 mm, H–M 0.1 mm.