Fossil Leaves Belonging to Family Annonaceae from Sub-Himalayan Zone (Siwalik) of Himachal Pradesh, India and their Climatic and Phytogeographical Implication

Investigation on the fossil leaves collected from Middle Siwalik sediments of Sarkaghat area, in the Sub-Himalayan zone of Himachal Pradesh revealed the presence of four new fossil species belonging to the family Annonaceae. The fossil leaves have been identified with the extant species, Annona reticulate Linn. Polyalthia longifolia (Son.) Thw. P. siamiarum (Buchanan-Hamilton ex Hooker and Thomson and cananga odorata Hook. f. and Th. The analysis of the current distribution of fossils' nearest living relatives (NRLs) shows that these species are currently found in the evergreen forests of northeastern and south-east Asia, rather than in and around the study area or throughout the sub-Himalayan zone of India. This suggests that after Miocene these taxa could not survive there and migrated towards south and south-east region. Based on the data available the phytogeographical aspect of these fossil taxa along with family Annonaceae has been discussed.