Leaf cuticular morphology of some angiosperm taxa from the Siwalik sediments (middle Miocene to lower Pleistocene) of Arunachal Pradesh, eastern Himalaya: Systematic and palaeoclimatic implications

Seven fossil leaves with cuticle described here were collected from the lower, middle and upper strata of Siwalik (middle Miocene-lower Pleistocene) sediments of Arunachal Pradesh, India. A detailed comparison of the cuticular analysis of the fossils and their living relatives indicate that these fossil species belong to Dysoxylum raptiensis, Macaranga cf. denticulata, Calophyllum suraikholensis, Combretum prechinense, Actinodaphne palaeoangustifolia, Shorea siwalika and Dipterocarpus koilabasensis. Among these fossil species C. prechinense has been described as a new species. The present day distribution of the modern equivalent taxa of the fossils, structural features and the micro-morphological features of the fossil leaves together with epiphyllous fungal remains collectively indicate the prevalence of a warm humid tropical climate in this area during Siwalik sedimentation. The cuticular micro-morphological features help to confirm the identification of their leaf compressions to the species level and are clearly indicative of mesophytic ecological conditions that reflect a tropical climate with high precipitation. This is the first time Cenozoic fossil leaves of Dysoxylum, Macaranga, Calophyllum, Combretum, Actinodaphne, Shorea and Dipterocarpus are described using the micromorphology of their epidermis.