First fossil evidence of samaras of Ailanthus Desf. (Simaroubaceae) from India and its implications

Abstract

Even though it is now widespread in Asia and was widely distributed in the Northern Hemisphere during the Cenozoic, fruits of the genus Ailanthus Desf. (Simaroubaceae) have not previously been documented from the Cenozoic of India. Here, we report the first Indian occurrence of fossil winged fruits corresponding to the modern genus Ailanthus having samaroid mericarps with a centrally placed seed from the latest Neogene sediments of Chotanagpur Plateau, eastern India. We determine their taxonomic position based on a detailed morphological comparison with similar modern and fossil specimens and discuss their palaeoclimatic significance. The fossil fruits are elongated, elliptic samaroid mericarps with a centrally placed seed and a marginal ventral vein starting from the seed extend to the base of the fruit. The fruits are 24–39 mm long and 11–16 mm wide. Based on the available morphological characters including locations of the stylar scar, main ventral vein, and the size of the samara, we assign these specimens to the fossil species Ailanthus confucii Unger. This species has a rich fossil record from the Cenozoic sediments of Europe, North America, and eastern Asia. However, this is the first report of A. confucii in India, which is significant for this species’s biogeographic and evolutionary history. Based on morphological comparisons, A. confucii shows affinity to modern A. altissima. Here, we also review the biogeographic history of Ailanthus and suggest its possible migratory routes.