Densoisporites polaznaensis sp. nov. with comments on its relation to Viatcheslavia vorcutensis Zalessky

Abstract

A new species of lycopsid microspores, Densoisporites polaznaensis., is described. The spores were extracted from clayey matrix containing stems and phylloids of Viatcheslavia vorcutensis Zalessky, a characteristic lepidophyte of the lowermost Upper Permian (Solikamskian) of the Ural Mountains and Russian Platform. The fossils studied came from the Polazna Locality of the Ufimian (Roadian) age, situated near Perm City, Russia. The spores of D. polaznaensis are 30-69 µm, round to subtriangular, having almost smooth proximal side with clearly visible trilete scar with rays extended to the spore equator. Distal side of the spores has a fine granulate relief, formed by widely spaced distinct granulae. The sporoderm is two-layered; the outer layer consists of numerous interlaced lamellae and the inner layer includes a single lamella. At some sections, in the central region of spores, "laminated zones" were detected in the inner layer. There is a weakly developed cavity in the sporoderm. Viatcheslavia vorcutensis is represented by wide stem fragments (up to 30 cm in diameter). Leaf cushions are present on old lowermost stem parts, but any attached phylloids/sporophylls were not found, the phylloids/sporophylls obviously were shed. Leaf cushions usually are round, with clear scar of leaf attachment and ligular depression on the upper margin of the cushion. Two small areas of parenchymatous tissues (possible parichnos) are occasionally seen. On the basis of cooccurrences and typological extrapolation with related taxa of lycophytes belonging to the family Pleuromeiaceae, it is suggested that microspores of Densoisporites polaznaensis were produced by Viatcheslavia vorcutensis. The palaeoecology of Viatcheslavia vorcutensis interpreted as a halophytic plant is discussed.