The Carboniferous microfungus Protoascon missouriensis has been interpreted variously as an ascomycete, chytridiomycete, zygomycete and oomycete. We offer a more complete interpretation based on a re-examination of the type material that suggests the fossil represents an (a)zygosporangium-suspensor complex of a zygomycete comparable to some modern members of the Mucorales.

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