Fertile pinnules of Danaeites rigida Gu and Zhi (Marattiales) from the Upper Permian of south China

Recently collected specimens of Danaeites rigida Gu and Zhi from the Upper Permian of south China have been subjected to detailed morphological investigations in order to reveal features of their fertile pinnules. The specimens are preserved as compression/impressions and possess pecopteroid-type pinnules with a single row of synangia on either side of the pinnule midvien. Individual synangia are bilaterally symmetrical, sessile, and their bases are embedded in the tissues of the pinnules. Synangia possess 18–24 sporangia that are laterally fused to one another throughout their entire length. Sporangial dehiscence is through a longitudinal slit and sporangia contain trilete spores with a granular ornamentation, referable to the dispersed spore Cyclogranisporites. This combination of characters is unique in specimens preserved by compression/impression although they are similar to those known in permineralized marattialean fertile fronds. However, anatomical details salient to the identification of these permineralized taxa are not identifiable in impression/compression fossils such as Danaeites. The taxonomic and phylogenetic implications of these findings are considered in detail and we conclude that Danaeites has closer links with Marattia than with Danaea.