The First Fossil Record of Coryphoid Palm from Siwalik Strata (Middle Miocene) of Darjeeling Foothills of Eastern Himalaya

Abstract

Although coryphoid fossil palms are well-known from the Upper Cretaceous sediments of India, there is no fossil evidence of coryphoid palms from Siwalik sediments to date. Here, we report for the first time coryphoid palm fronds from the lower Siwalik strata (Chunabati Formation; middle Miocene) of Darjeeling foothills of eastern Himalaya. The leaf architecture, as well as the epidermal anatomy of the Siwalik specimens, suggests their resemblance with those of extant members of the palm sub-family Coryphoideae. The Siwalik specimens are characterized morphologically by palmate fan-shaped leaf with a well-preserved costa (costapalmate), prominent leaf segments emerging at an acute angle from the costa, numerous parallel secondary lateral veins on either side of the mid-vein, and anatomically by hypostomatic leaf blade, rectangular to polygonal epidermal cells, cyclocytic type of stomata and the presence of characteristic trichome bases. Based on a thorough comparison with earlier reported coryphoid palm leaves bearing epidermal anatomy, we placed our specimens under a new fossil species Sabalites siwalicus sp. nov. that is also supported by cluster analysis. The present fossils indicate that coryphoid palms were present in eastern Himalaya by the Siwalik time and they experienced a warm and humid tropical environment during the time of deposition.