Fossil wood of Terminalioxylon (Combretaceae) from the Late Miocene of Southeastern Pakistan: Biogeographic and paleoecological implications

Fossil wood from the Late Miocene of Manchar Formation in the Lower Indus Basin, the Sindh Province, Pakistan has been attributed to Terminalioxylon sp. (cf. T. eo-olivari Harsh, Sharma & Suthar) (Combretaceae). This is the first fossil evidence of this family from the Manchar Formation, exposed in the Lower Indus Basin. Terminalioxylon sp. (cf. T. eo-olivari) is characterised by the combination of the lack of growth rings, small to large intervessel pits, abundant aliform and aliform-confluent axial parenchyma, the lack of septate fibres, exclusively uniseriate rays, and the occurrence of prismatic crystals in ray cells. The mesomorphic wood traits, including vessels (75-173 μm in tangential diameter, 6.4-7.2 per mm²) and abundant axial parenchyma, suggest that T. sp. (cf. T. eo-olivari) might be a large tropical or subtropical forest tree species. This fossil wood species provides new evidence for the forest vegetation in what is now Sindh Province during the Late Miocene. Forests predated the expansion of grassland, which occurred about 8 Mya in this region, due to global cooling and local aridification after the Middle Miocene Climatic Optimum.