Vizellopsidites siwalika, a new fossil epiphyllous fungus from the Plio-Pleistocene of Arunachal Pradesh, eastern Himalaya

The present article reports the in situ occurrence of a new fossil epiphyllous fungus Vizellopsidites siwalika gen. et sp. nov. on the abaxial cuticular surface of fossilized leaf fragments of the angiosperm Dysoxylum raptiensis Prasad & Awasthi (Meliaceae) from the upper Siwalik sediments (Kimin Formation, late Pliocene to early Pleistocene) of Arunachal Pradesh, eastern Himalaya. The fungus features a well-preserved unique mycelium composed of short, brown, squarish to rectangular hyphal cells with conspicuously thickened dark septa. The fungal colonies also include a small, circular sporoma formed of isodiametric dark-brown cells with thick, dark septa and a central circular ostiole. as well as scattered spherical to broadly ovate, 1-celled, brown spores. The in situ evidence of Vizellopsidites on Dysoxylum leaflet indicates that a possible host-ectoparasite relationship existed in the ancient warm and humid tropical evergreen forest of Arunachal sub-Himalaya during the Plio-Pleistocene time.