Fossil Asterinaceae in the phyllosphere of the eastern Himalayan Neogene Siwalik forest and their palaeoecological significance

This study presents six new species of Asterina (Asterinaceae), A. indodeightonii, A. mioconsobrina, A. miosphaerelloides, A. neocombreticola, A. neoelaeocarpi and A. presaracae, on fossil angiosperm leaf remains recovered from the Siwalik sediments (mid-Miocene to early Pleistocene) of Arunachal Pradesh, eastern Himalaya. On the basis of leaf architecture, host leaves resemble the modern genera Actinodaphne (Lauraceae), Anthocephalus (Rubiaceae), Combretum (Combretaceae), Lindera (Lauraceae), Unona (Annonaceae) and one unidentified dicotyledonous plant. The in situ occurrence of Asterinaceae on these angiosperm leaf remains suggests diverse fungal associations in the phylloplane of ancient evergreen-deciduous tropical forest of Siwalik. The diversity of Asterinaceae also supports the rise of plant pathogenic forms during the mid-Miocene to early Pleistocene for which host plant diversity and environment may have played significant roles. Similar host parasitic interactions in modern Asterina spp. further support a co-evolutionary trend since the Neogene in Asterinaceae.