An old saddle
The Dryads were out riding in the forest last night and have left some of their saddles behind. In reality this is the polypore fungus known as the Dryad's saddle fungus Polyporus squamosus.
The generic name Polyporus means 'many pores' whilst the specific epithet squamosus means 'scaly'. A Dryad is a tree nymph or tree spirit in Greek mythology. You can see one here.