Earliest megafossils of scandent calamoid palms from the Deccan Intertrappean Beds of Central India and their paleobiogeographic implications

Abstract

Two well-preserved petrified palm stems from the latest Maastrichtian (Late Cretaceous) to earliest Danian (Early Paleocene) sediments of the Deccan Intertrappean Beds of Madhya Pradesh, Central India are described. Their significant anatomical characteristics include a Calamus-type general stem pattern, the presence of well-preserved fibrovascular bundles (fvbs) with two wide metaxylem vessel elements (230 μm–250 μm) and one phloem strand, uniform density of fvbs, lack of continuity between protoxylem and metaxylem vessel elements, and an absence of centrifugal differentiation of sclerenchymatous fibrous parts. These features reveal a close resemblance to those of extant genera of scandent Calamoideae. The permineralized stems are described as a new species namely, Palmoxylon calamoides Kumar, Roy et Khan sp. nov. The fossils represent the oldest reliable fossil records of this family, supporting their Gondwanan origin, their importance in tracing their migration pathways from India to Europe and other continents after the docking of the Indian subcontinent with Eurasia during the Paleocene, and an “Out-of-India” dispersal hypothesis. Today the subfamily Calamoideae is disjunctly occurred in Africa, Asia, Australia, Europe, and South America, but the poor deep-time fossil record of this subfamily with a small number of Cenozoic fossils makes hypotheses concerning its origin and dispersal difficult to evaluate. The present study has significant implications for the origin and migration of this subfamily and the paleoclimate.