A new species of structurally preserved fern rhizome,Ashicaulis dumbbella sp.nov.(Osmundaceae) is described from the Jurassic fossil Lagerst(a)tte in western Liaoning,NE China.The new species is represented by a rhizomatous stem,composed of a pith,an ectophloic dictyoxylic siphonostele,a two-layered cortex and a mantle of petiole bases and adventitious roots.The pith is 3.0-4.5 mm in diameter.The xylem cylinder consists of approximate 20 xylem strands separated by definite immediate leaf gaps.The leaf trace is adaxially concaved;with one single endarch protoxylem cluster which first bifurcating in the petiolar zone.The new species characterized itself by a remarkable specialized petiolar structure,,a heterogeneous sclerotic ring with the abaxial side occupied by a dumbbell-shaped thick-walled fiber arch.The new fossil species ofA.dumbbella sp.nov.contributes to further understand the petiolar anatomical diversity of the Mesozoic permineralized osmundaceous plants in the Northern Hemisphere.Some fungal remains,represented by branched hyphae are found within the rhizome,which represents the first report of fossil fungal remains preserved in the Mesozoic osmundaceous rhizomes,as well as the first record of Jurassic fungi in China.These fungal remains are proposed to be ecologically saprotrophic with evidences of typical wood rotting structures in the host.