Fossil woods from the late middle Eocene Pondaung Formation, Myanmar

Twelve species of fossil wood were identified from silicified specimens collected in the late middle Eocene Pondaung Formation, Myanmar. These species display affinities with modern Fabaceae, Moraceae, Combretaceae, Sapindaceae, Malvaceae, Dipterocarpaceae and Theaceae. They include five new species of the fossil genera Ficoxylon (F. mogaungense sp. nov.), Sapindoxylon (S. burmense sp. nov.), Bombacoxylon (B. pondaungense sp. nov.), Shoreoxylon (S. panganense sp. nov.) and Schimoxylon (S. benderi sp. nov.). This material represents the oldest record of fossil dipterocarps so far reported outside the Indian subcontinent. It reflects different ecotones of a dry dipterocarp forest, with coastal, riparian, and inland elements. The Burmese fossil assemblage further contrasts with the common idea that lowland rainforests were widespread in Southeast Asia during the Eocene. It suggests that the climate in the proto-Bengal Bay was more seasonal than previously thought. This confirms that early Dipterocarpaceae were adapted to seasonally dry climates, despite the modern prevalence of warm humid tropical species. •We identify twelve fossil wood species in the late middle Eocene deposits of Myanmar.•Floral assemblage includes fossil Shorea-like dipterocarps.•Floral assemblage reflects different ecotones of a dry dipterocarp forest.•Middle Eocene climate in the proto Bengal Bay was significantly seasonal.•Dipterocarps were early adapted to seasonal climates.