A new meliolaceos foliicolous fungus from the Plio-Pleistocene of Arunachal Pradesh, eastern Himalaya

Abstract We report in this article, the in situ occurrence of a new species of Meliolinites (fossil Meliolaceae), Meliolinites neogenicus sp. nov. on the abaxial cuticular surface of fossilized leaf cuticle fragments of the angiosperm Litsea cf. salicifolia Khan et al. (Lauraceae) recovered from the upper part of the Siwalik succession of Neogene sediments (Kimin Formation: late Pliocene to early Pleistocene) of Arunachal Pradesh, eastern Himalaya, India. This Plio-Pleistocene melioloid foliicolous fungal morph features a well-preserved unique mycelium consisting of superficial, dark brown, thick-walled and branching hyphae with bicellular appresoria and unicellular phialides. The fungal colonies also include globose, dark brown perithecia, as well as one ellipsoidal, 5-celled, 4-septate, dark brown ascospore. The fossil leaf of Litsea , together with the foliicolous fungal remains indicates the prevalence of a warm, humid, climate in the Arunachal sub-Himalaya during the Plio-Pleistocene. The in situ evidence of Meliolinites on host leaf cuticle indicates the possible existence of a host–ectoparasite relationship in the ancient warm and humid tropical evergreen forest of this area during the Plio-Pleistocene. Based on present and earlier records it is suggested that Lauraceae has been a common host for meliolaceous fungi since the early Cenozoic. Meliolinites neogenicus sp. nov. might have thrived under a warm and humid climate with a mean annual temperature (MAT) from 21 to 26 °C and a mean annual precipitation (MAP) from 1000 to 2000 mm in the Plio-Pleistocene of Arunachal sub-Himalaya which is in conformity with our earlier published qualitative and quantitative climatic data.