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Fabaceous macro fossils from Siwalik foreland basin of Mandi district, Himachal Pradesh, India and their phytogeographic and climatic implications
MAHESH PRASAD, ALOK, SHIVENDRA MOHAN PANDEY and SHASHI
Abstract
A detailed investigation of the plant macrofossils (leaf impression, fruit, and seed) from the Middle Siwalik sediments of Sarkaghat, Mandi District, Himachal Pradesh, India, revealed the occurrence of four new fossil taxa comparable to Mezoneuron hymenocarpum W.&A. ex Prain, Dialium indum Linn., Acacia caesia W.&A. and Entada phaseoloides Benth. of the family Fabaceae. The fossil leaves are characterized by compound, asymmetrical elliptic to narrow elliptic shapes, entire margin, eucamptodromous venation, and the presence of inter secondary veins. The fruit is a loment type having narrow ends, and there is the occurrence of a single, small, almost circular seed in each segment. In contrast, the seed is characterised by a circular to orbicular shape with a pronounced depression at the hilum. The comparable taxa of the macrofossils (except E. phaseoloides Benth.) are presently not found to grow in and around the Sarkaghat as well as in the Himalayan foothills of Himachal Pradesh, India but are found distributed in the tropical evergreen forests of other suitable phytogeographical regions which may suggest that tropical evergreen forests under warm, humid climate with heavy rainfall were in existence during the Upper Miocene in this region in contrast to a mixed deciduous forest under the tropical climate with aridness.
Keywords: Morphotaxonomy, Macrofossils, Fabaceae, Middle Siwalik, Phytogeography, Palaeoclimate, Himachal Pradesh, India
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