''Bartheletia paradoxa'' is a species of

dimorphic fungus Dimorphic fungi are fungi that can exist in the form of both mold and yeast. This is usually brought about by change in temperature and the fungi are also described as thermally dimorphic fungi. An example is ''Talaromyces marneffei'', a human ...

and is the only member of the genus ''Bartheletia''. ''Bartheletia'' is the only genus in the family Bartheletiaceae, which is the only family in Bartheletiales, which in turn is the only order in the class Bartheletiomycetes. Sorus-like sporodochia form on freshly fallen leaves and petioles of ''

Ginkgo biloba ''Ginkgo biloba'', commonly known as ginkgo or gingko ( ), also known as the maidenhair tree, is a species of tree native to China. It is the last living species in the order Ginkgoales, which first appeared over 290 million years ago. Fossils ...

'' in early autumn in Asia and Europe and persist through the winter. They produce slimy, hyaline 1-celled, cylindrical conidia. Thick-walled, dark brown teliospores develop in leaf tissue, clustered in structures ~1 mm diam, similar to telia of rust fungi, causing black leaf spots surrounded by a gray halo. After a year of dormancy, long-stalked basidia emerge through an apical channel from each teliospore, becoming round, cruciately-septate, and producing a succession of cylindrical basidiospores from four wart-like loci. Cultures can be isolated from discharged basidiospores or conidia spread on standard agar media. Like its host ''G. biloba'', ''B. paradoxa'' has no closely related (living) relatives and is considered a "living fossil".

References

Agaricomycotina Monotypic fungi genera {{Agaricomycotina-stub