A new permineralized osmundaceous rhizome with fungal remains from the Jurassic of western Liaoning, NE China

Abstract Diverse plant fossils have been reported from the fossil Lagerstatte in the Middle to Upper Jurassic Tiaojishan Formation in Liaoning Province, Northeast China. However, structurally preserved fossil plants that bear fungal remains are quite rare in this region. Here, we report a new permineralized fern rhizome, Claytosmunda zhangii sp. nov. (Osmundaceae, Osmundales), from the Tiaojishan Formation in Beipiao of western Liaoning Province. The fossil specimen is represented by a rhizomatous stem consisting of a pith, a dictyoxylic siphonostele, a two-layered cortex, and a mantle of petiole bases. A remarkably specialized heterogeneous petiolar sclerotic ring, whose abaxial side is occupied by a dumbbell-shaped thick-walled fiber arch, characterizes this new fossil species. The anatomical diversity of petiolar sclerotic rings of Mesozoic and extant osmundaceous plants is discussed in this study. Five major types of petiolar sclerotic rings are recognized. Fungal remains, represented by branched hyphae, are found within the fern rhizome. To our knowledge, this is the first report of fungal remains associated with osmundaceous rhizomes in China. Paleoecologically, these fungal remains are tentatively interpreted as a kind of saprophytes.