Chansitheca wudaensis (Gleicheniaceae, fern) from the early Permian Wuda Tuff Flora, Inner Mongolia

A large number of specimens of Chansitheca wudaensis Deng, Sun et Li from the early Permian Wuda Tuff Flora allow an emendation of this species. Characters of the sporangial structure and in situ spores are examined for the first time. Sori are arranged on lateral veins of pinnule lobes, and are 0.61–0.69 mm long and 0.35–0.41 mm wide. Sporangia are sessile and surrounded by an annulus, which is composed of two rows of oblong thick-walled cells. Trilete, smooth in situ spores have diameters of 21.05–26.31 μm. Features of the reproductive organ indicate that this species is similar to Szea Yao et Taylor and some species of Oligocarpia Goeppert and belongs to the Gleicheniaceae. Based on a taphonomical analysis, C. wudaensis was an herbaceous element of the groundcover in the peat-forming coal swamp.