FOSSIL XYLARIACEAE SPORES FROM THE CRETACEOUS AND TERTIARY SEDIMENTS OF NORTHEASTERN INDIA
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Abstract:
Diverse type of fossil xylariaceous single furrowed amerospores, such as Hypoxylonites and Spirotremesporitesare recorded from the Cretaceous and Tertiary sediments of northeastern India. About 15 species of Hypoxylonites have beenidentified of which 6 are new suchas H. bhubanensis, H. elsikii, H. minimus, H neogenicus, H. subrotundus and H. thindii.Stratigraphic data reveal the appearance of Hypoxylonites in this area during the late Cretaceous composing no more than 3%-4% of the total microflora. In the Eocene, they became more abundant covering almost 20%-25% of the total assemblage.Greatest diversity that occurs at the onset of Miocene constituting 40%-45% of the total assemblage retains up to the earlyPliocene. Frequency of occurrence dropped sharply in the late Pliocene sediments. Speceis of another form genusSpirotremesporites are absent in the Cretaceous strata. However, they appeared in this area during the Late Eocene and com-posing only 5%-6% of the total spore-pollen assemblage. The taxa became moderately diversified during the Miocene, com-posing 25%-30% of the microflora and declined at the end of Pliocene. Five new species of Spirotremesporites have beenrecorded and these are Spirotremesporites ellipticus, S. longiletus, S. miocenicus, S. reniformis and S. tertiarus. Comparisionof these taxa with the spores of different species of Xylaria, Hypoxylon, Rosellinia and Daldina and their stratigraphic distri-bution pattern indicate the evolutionary history of the group which probably was controlled by the climatic factors of thebasinal area.
