in may 2019, scientists reported the discovery of a fossilized fungus, named "ourasphaira giraldae", in the canadian arctic, that may have grown on land a billion years ago, well before plants were living on land. earlier, it had been presumed that the fungi colonized the land during the cambrian (542–488.3 ma), also long before land plants. fossilized hyphae and spores recovered from the ordovician of wisconsin (460 ma) resemble modern-day glomerales, and existed at a time when the land flora likely consisted of only non-vascular bryophyte-like plants. prototaxites, which was probably a fungus or lichen, would have been the tallest organism of the late silurian. fungal fossils do not become common and uncontroversial until the early devonian (416–359.2 ma), when they are abundant in the rhynie chert, mostly as zygomycota and chytridiomycota. at about this same time, approximately 400 ma, the ascomycota and basidiomycota diverged, and all modern classes of fungi were present by the late carboniferous (pennsylvanian, 318.1–299 ma).