The in situ spore ultrastructure of fossil Marattia asiatica (Kawasaki) Harris, a common Early Mesozoic marattialean fern in Asia, is investigated using scanning and transmission electron microscopes based on the material from the Lower Jurassic Hsiangchi Formation in Hubei, China. The exospore consists of a thin inner layer, a thick homogeneous outer layer, and an intermediate zone (middle layer). The intermediate zone comprises some very thin sheets linked to the inner layer and interbedded with sporopollenin similar to that composing the outer layer and includes small cavities connected to the wall surface through narrow canals crossing over the outer layer. No perispore elements were observed in the investigated spores. Comparisons of the exospore ultrastructures, especially those of the intermediate zone in extant and fossil ferns, indicate close affinities between fossil M. asiatica and the extant Marattiaceae. Such affinities are less evident for the Paleozoic fossil record of marattialeans, probab...