A New Fossil Black Mildew Revealing Biotrophic Mycoparasitism on a Callimothalloid Fungus from the Miocene Siwalik of India

Mycoparasitism, a phenomenon in which certain fungi parasitize other fungi, is quite prevalent in nature; however, it remains poorly studied. Nowadays, this type of interaction is commonly used to suppress pathogen populations and to facilitate biological control of plant diseases. Nevertheless, examination of this phenomenon in the fossil record is exceedingly uncommon, which hinders our comprehension of the evolution and diversity of fungi, along with their interactions. Here, we report and describe a new fossil fungal species, Meliolinites mycoparasitica sp. nov. (Meliolaceae), together with another ascomycetous fungus, Neomycoleptodiscus pertusus , (Muyocopronaceae), on a host plant (cuticular fragments of a compressed dicotyledonous leaf resembling modern Quercus spp., Fagaceae) recovered from middle Siwalik sediments (Late Miocene, ca. 12–8 My) of Himachal Pradesh, western Himalaya. This represents the first fossil evidence of tritrophic interactions involving M. mycoparasitica as a mycoparasitic fungus, N. pertusus as a fungal host, and Quercus sp. as a host plant. This finding provides a unique opportunity to explore the mycoparasitic nature of the melioloid fungus within the context of paleomycological research.