Biternatisporites compositus (Mashchuk) Mashchuk, 2022

Mashchuk, Irina M. & Frolov, Аndrey O., 2022, Biternatisporites gen. nov. - a new megaspore genus from the MiddleCarboniferous sediments of the Tunguska basin (Siberian platform, Russia), Phytotaxa 576 (2), pp. 227-232 : 229-230

Biternatisporites compositus (Mashchuk) Mashchuk , comb. nov. ( Fig. 3 )

Basionym: — Aphanozonatisporites compositus Mashchuk (2010: 58)

Type:— RUSSIA, Siberia: north-east of the Tunguska Basin , Malo-Botuobinsky region, place Chaidakh, N 62°35’26”.599, E 112°49’19”.805, Lapchan Formation, Middle Carbon (Bashkir and Moscow stages), hole 690, line 475.5, depth 148 m (holotype no. 56-2; Institute for Earth’s Crust, Siberian Branch of the Russian Academy of Sciences) .

Specific diagnosis:—as for the genus.

Description:—Megaspores circular-triangular to irregular-triangular; diameter 750–850 μm. Trilete tetrad scar mark represented by short roll lying on original base, consisting of tree robust rays with straight angles; length of one ray 350 μm. Edges of rays reach megaspore margin and ends of small rays with length of 150 μm merge into angles of large rays, forming system of double rays. Structure of small rays of dehiscence mark heteroalveolate-connected with punctate fossae on surface of lumina. Structure of large rays foveolate-tuberculate.

Etymology:—from Latin word compositus = ‘composite’.

Comparison:—The type species of Biternatisporites is almost similar to the species Aphanozonatisporites glabratus ( Zerndt 1930: 43) Oshurkova (2001: 25) , but the species of the new genus differs in its larger size and the absence of the areola for the small rays.

Figures

FIGURE 3. Biternatisporites compositus gen. & comb. nov. A–E. General view of megaspores. A. Specimen no. 65, magnification ×42. B. Specimen no. 68, magnification ×42. C. Specimen no. 70 (holotype), magnification ×49. D. Specimen no. 70 (holotype), magnification ×185. E. Specimen no. 71, magnification ×58. F. Structure of large rays, specimen no. 70 (holotype), magnification ×2200. G. Structure of small rays, specimen no. 70 (holotype), magnification ×2200. Photographer: Iochannes Moeller, Alfred Wegener Institute for Polar and Marine Research, Potsdam.