Fossil palm fruits from India indicate a Cretaceous origin of Arecaceae tribe Borasseae

Abstract

The fossil record of palms (Arecaceae) is essential for understanding the deep evolutionary and geographical history of the family. We studied palm fruit fossils from the c. 67-64-Myr-old Deccan Intertrappean Beds of India to infer the systematic relationships of the fossils and their relevance to palm evolution. Using X-ray micro-computed tomography, physical sectioning techniques and a total-evidence phylogenetic analysis, we show that these fossils represent a crown group member of subtribe Hyphaeninae (tribe Borasseae, subfamily Coryphoideae) allied with the extant genera Satranala and Bismarckia, now endemic to Madagascar. These fossils, synonymized here as Hyphaeneocarpon indicum, provide evidence for the existence of crown group Hyphaeninae during the late Maastrichtian-early Danian. This pre-dates prior age estimates for the Hyphaeninae crown node by nearly 40 Myr and implies an earlier divergence of Borasseae. The presence of Hyphaeneocarpon in India shows that Borasseae have persisted in the Indian Ocean region for > 64 Myr. This study illustrates the utility of palm fruit characters for placing fossils in a phylogenetic context and has important implications for understanding the evolution and diversification of Borasseae and the palaeobiogeography of palms.