Sprecher
Beschreibung
This study describes a new fossil wood species, Pahudioxylon pakistanicum Izhar, Su and Oskolski, n. sp. from the Middle to the Upper Miocene Kamlial Formation in the Salt Range, eastern Pakistan. This is the first fossil record of the subfamily Detarioideae (Fabaceae) in Pakistan. The new species is characterized by a combination of simple perforation plates, small to medium alternate intervessel pits, lack of septate fibres, vasicentric, aliform and confluent axial parenchyma, occasionally in interrupted marginal bands, irregularly storied homocellular rays, and the occurrence of prismatic crystals in the chambered axial parenchyma cells. This fossil wood is most similar to Dichrostachyoxylon and Pahudioxylon, which are linked to modern detarioid Afzelia and Intsia. The presence of storied rays, however, indicates its closer affinity with Detarioideae rather than mimosoid taxa, confirming its placement in Pahudioxylon. Meanwhile, this finding suggests a vagueness of generic delimitation between Pahudioxylon and Dichrostachyoxylon. The mesomorphic wood traits (indistinct growth rings, wide vessels, abundant axial parenchyma) suggest that P. pakistanicum was likely a large tree species growing in the tropical or subtropical forests. This fossil record provides the first evidence of such a vegetation type of forest in the Salt Range region during the Middle to Late Miocene, prior to the onset of aridification and the expansion of grasslands in the Himalayan foreland basin approximately 8 million years ago.