Fossil woods from the lower Miocene of Myanmar (Natma Formation): paleoenvironmental and biogeographic implications
Résumé
The paleobotanical record of Myanmar is poorly documented despite its importance for understanding the evolution of Asian monsoonal ecosystems through time. Here, we describe seventeen species of fossil wood from silicified specimens collected in the upper lower to lowermost middle Miocene Natma Formation, central Myanmar. These species share affinities with modern Fabaceae, Dipterocarpaceae, Burseraceae, Moraceae and Cupressaceae. Five new species are described, belonging to genera KoompassioxylonKramer (K. kalewensis n. sp.), Pahudioxylon Chowdhury, Ghosh & Kazmi (P. adenantheroides n. sp.), Dipterocarpoxylon (Holden) Den Berger (D. fugax n. sp.), ShoreoxylonDen Berger(S. glomeratum n. sp.), Artocarpoxylon Prakash& Lalitha (A. informe n. sp.). They include the first record of genus Dryobalanoxylon Den Berger in Myanmar, as well as a great variety of fossil dipterocarps (7 species) as found in today’s Southeast Asian rainforests. The nearest living relatives of this assemblage reflect different ecotones of seasonal forests with coastal, mixed to dry deciduous, and wet evergreen species. This reconstruction implies a wet, warm, and monsoonal climate in Myanmar during the late early Miocene. The presence of fossil dipterocarp species typical of wet evergreen forests contrasts with Burmese Eocene dry dipterocarp assemblages and indicates wetter conditions during the Miocene. Our reconstructions support a long-term change from seasonal to everwet ecosystems for dipterocarp trees.
Origine : Fichiers produits par l'(les) auteur(s)