Two new species of suspected mushrooms of the suborder Marasmiineae from mid-Cretaceous Burmese amber (Basidiomycota, Agaricales)

Although mushrooms are important components of ecosystems, their large-scale evolutionary history patterns are rarely known, mainly due to the limited fossil record and the lack of comprehensive phylogenetic studies. Here we present and depict two new species of mushrooms, Marasmiamimum cretaceum gen. et sp. nov. and Mesoagaracites burmitis gen. et sp. nov., based on amber specimens from the mid-Cretaceous period in Kachin State, Myanmar, suspected to belong to the Marasmiineae suborder. The two genera exhibit limited traits, such as ultraminiature basidiomata, a broadly convex pileus with a smooth surface and slightly incurved margin, and sparse lamellae, make it challenging to categorize them into exact families. Similar characteristics are also found in the family Agaricaceae, Mycenaceae, and Omphalotaceae. These new findings enhance our understanding of mid-Cretaceous mushroom biodiversity during the Mesozoic. Furthermore, we provide a catalog of mushroom records in deep time.