Calophyllum L.: An important tropical element in the monsoon-influenced ancient Siwalik Forest of eastern Himalaya

Abstract

Calophyllum vegetative (leaves and woods) fossil remains have been widely reported from the Cenozoic sedimentary strata across the Northern and Southern Hemispheres. However, until now, no reproductive megafossil remains have been discovered. Here, we report and describe Calophyllum fossil fruits from the Siwalik (middle Miocene–Pliocene) sediments of Darjeeling foothills, eastern Himalaya for the first time. In addition, we also provide fossil materials of isolated leaves in appreciable numbers recovered from the same stratigraphic level. Our Siwalik fossils and extant members of Calophyllum are closely related morphologically by stalked, ball-shaped (spherical to ovoid) drupe with a thin, dark brown, smooth surfaced outer layer and a hard endocarp; and symmetrical, oblong-elliptic shaped entire margined lamina with numerous close parallel secondary veins, and obscure tertiary veins. Based upon morphology and epidermal anatomy, the fossil fruits are recognized as a new fossil-species Calophyllum ramthiensis sp. nov. The present Calophyllum leaf and fruit fossils, along with previous reports suggest that Calophyllum was an important forest element throughout the eastern Himalaya during the period of Siwalik sedimentation (Mio-Pleistocene time). We briefly discuss the fossil history of Calophyllum and palaeobiogeography in India and palaeoclimatic implications regarding the distribution and habitat of fossil and modern members of Calophyllum.