A new leptosporangiate fern Oligosporangiopteris zhongxiangii gen. and sp. nov. from the lowermost Permian of Inner Mongolia, China - morphology, anatomy and reproductive organs

This study focuses on a new leptosporangiate fern Oligosporangiopteris zhongxiangii gen. and sp. nov. from the in situ tuff flora located in the upper part of the Taiyuan Formation (lowermost Permian), Wuda coalfield, Inner Mongolia, North China. We propose a whole-plant concept based on specimens that represent various parts of the plant. Petioles of the new fern are characterized by a tangentially elongated, slightly curved, bar-shaped xylem strand that has four protoxylem strands on the concave side. Protoxylem strands occur in pairs located close to the lateral xylem ends and the xylem has endarch maturation. The pinna rachis shows a similar anatomy, whereas pinnules are of the cladophleboid type bearing Oligocarpia type of sporangia: sori consisting of 4-8 sporangia. The microspores represent the smallest in situ record of the genus Granulatisporites. The unique combination of the rachial anatomy together with the reproductive organs with in situ spores justifies the creation of Oligosporangiopteris zhongxiangii gen. and sp. nov. In addition, the new combination Oligocarpia wudaensis (Deng, Sun and Li) comb. nov. is proposed.