New fossil leaves of Annonaceae and Achariaceae from Churia Group of Nepal and their phytogeographical implications

Study on the fossil leaves recovered from Churia Group of Arjun Khola area, western Nepal revealed the occurrence of five new fossil species, four belonging to the family Annonaceae and one to Achariaceae. The analysis of present day distribution of the comparable extant species, Unona longiflora Roxb., Annona reticulata Linn., Goniothalamus macranthus (Kurz) Boerlage, Artabotrys speciosus Kurz and Ryparosa caesia Blume ex Baill of fossils indicates that they do not grow in and around the study area as well as sub–Himalayan zone of India and Nepal but are presently distributed in the evergreen forests of north–east and south India and South–east Asian region. This suggests that after Miocene these taxa could not survive there most probably due to onset of drier conditions. Based on the data available the phytogeographical aspect of these fossil taxa of both the families has also been discussed.