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 Mahasin Ali Khan a , Subir Bera a, ⁎, Ruby Ghosh b , Robert A. Spicer c,d , Teresa E.V. Spicer d a Centre of Advanced Study, Department of Botany, University of Calcutta, 35, B.C. Road, Kolkata 700019, India b Birbal Sahni Institute of Palaeobotany, 53, University Road, Lucknow 226007 U.P., India c Environment, Earth and Ecosystems, Centre for Earth, Planetary, Space and Astronomical Research, The Open University, Milton Keynes MK7 6AA, UK d Institute of Botany, The Chinese Academy of Sciences, 20 Nanxincun, Xiangshan, Beijing 100093, China abstract article info Article history: Received 3 May 2013 Received in revised form 29 September 2014 Accepted 26 October 2014 Available online 15 December 2014 Keywords: Siwalik Middle Miocene–lower Pleistocene Arunachal Pradesh Fossil leaf Cuticle 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 cutic- ular 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 re- mains collectively indicate the prevalence of a warm humid tropical climate in this area during Siwalik sedimen- tation. 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. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Siwalik sediments are made up of rock materials eroded from the Himalayan Mountains deposited to the south on the flood plains of the foreland basins. The Siwalik sediments are characterised by the alternate presence of sandstone and mudstone facies, with the finer sediments very often containing abundant angiospermous fossils. During the last three decades several workers have recovered enormous number of leaf megafossils from the Siwalik foreland basins (Antal and Awasthi, 1993; Prasad, 1994a,b,c, 2006, 2008; Joshi and Mehrotra, 2007; Khan et al., 2011). By studying the plant fossils from Siwalik foreland basins it is possible to reconstruct Siwalik floristic evolution and to throw light on climatic changes that took place through Siwalik succes- sion (middle Miocene–lower Pleistocene) along the length of the Himalayan foothills. The fossil leaf assemblages indicated that in the Himalayan foothills luxuriant, tropical forests, rich in a diversity of angiospermous taxa flourished during middle Miocene–lower Pleisto- cene times (Prasad, 2008; Khan et al., 2011). Cuticular analysis is an important and proven tool for the identifica- tion of fossil leaves to lower (more precise) taxonomic levels (Johnson and Gilmore, 1921; Bandulska, 1923, 1926, 1931; Kräusel, 1938; Kvaček and Walther, 1981, 1984; Kovar, 1982; Kvaček, 1984; Liu, 1990; Vickulin, 1999; Zhuang et al., 2002; Wei et al., 2005; Hably and Kovar-Eder, 2006; Hu et al., 2007; Kovar-Eder and Sun, 2009; Li et al., 2009). However, until now cuticular studies of Cenozoic leaf remains from India have been rare. Cuticular analysis of angiosperm fossil leaves has been carried out previously from only two localities in India: late Holocene sediments of Himachal Pradesh (one taxon, Prasad et al., 2002) and upper Pliocene to lower Pleistocene sediments of Arunachal Pradesh (one taxon, Joshi et al., 2003). Cuticular anatomy of angiosperm leaf megafossils from Siwalik sediments is reported only from Arunachal Pradesh, India (Joshi et al., 2003) and Nepal (Prasad and Khare, 2004). A reliable determination of the fossil leaves to the species level is not possible without cuticular analysis. So, leaf taxa reported from the different Siwalik strata based on macromorphology exclusively (Antal and Awasthi, 1993; Prasad, 1994a,b,c, 2006, 2008; Joshi and Mehrotra, 2007; Khan et al., 2011) need to be revised and until then should be considered as preliminary. For this reason the most comprehensive approach is to identify leaf taxa using both epidermal characters preserved in the fossil cuticle in conjunction with macromorphological Review of Palaeobotany and Palynology 214 (2015) 9–26 ⁎ Corresponding author at: Department of Botany, University of Calcutta, 35, Ballygunge Circular Road, Kolkata 700019, India. Tel.: +91 33 2461 4959/5445x297 (O); fax: +91 33 2461 4849. E-mail address: berasubir@yahoo.co.in (S. Bera). http://dx.doi.org/10.1016/j.revpalbo.2014.10.008 0034-6667/© 2014 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Review of Palaeobotany and Palynology journal homepage: www.elsevier.com/locate/revpalbo