Abstract
Fossil leaflet impression described here as a new species Rourea miocaudata sp. nov., showing close resemblance with the modern leaflets of Rourea caudata Planch. (Connaraceae R. Br.), has been recorded from the lower part of the Siwalik sediments (Dafla Formation, middle–upper Miocene) exposed at the road-cutting section of Pinjoli area in West Kameng district, Arunachal Pradesh. The important morphological characters of the fossil are its narrow elliptic leaflet, cuneate base, long caudate apex, entire margin, eucamptodromous to brochidodromous secondary veins, presence of intersecondary veins, percurrent and reticulate tertiary veins and orthogonally reticulate quaternary veins. This is the first authentic record of the occurrence of leaflet comparable to R. caudata of Connaraceae from the Cenozoic sediments of India and abroad. At present R. caudata does not grow in India and is restricted only in southeast Asia especially in China and Myanmar. This taxon probably migrated to these southeast Asian regions after lower Siwalik sedimentation (middle–upper Miocene) due to climatic change caused by post-Miocene orogenic movement of the Himalaya. The recovery of this species and other earlier-described evergreen taxa from the same formation, suggests the existence of a tropical, warm and humid climatic conditions during the depositional period.
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Acknowledgements
We acknowledge Department of Science and Technology, New Delhi (SR/S4/ES-67/2003) for financial assistance. We are thankful to Mr Sambhu Chakraborty, Senior Geologist, Geological Survey of India, Itanagar for help and cooperation during the collection of samples. Thanks are due to the authorities of Central National Herbarium, Sibpur, Howrah for permission to consult the Herbarium.
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KHAN, M.A., BERA, S. First fossil evidence of Connaraceae R. Br. from Indian Cenozoic and its phytogeographical significance. J Earth Syst Sci 125, 1079–1087 (2016). https://doi.org/10.1007/s12040-016-0711-0
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DOI: https://doi.org/10.1007/s12040-016-0711-0