在印度东北部白垩纪-第三纪沉积中发现了各种类型单沟无隔壁的Xylariaceae化石孢子,例如:Hypoxylonites,Spirotremesporites.Hypaxylonites等共计15种,其中6新种,它们是Hypoxylonites bhubanensis,H.elsikii,H.minimus,H.neogenicus,H.subrotundus和H.thindii,Hypoxylonites在本地区一般出现于晚白垩世地层中,占化石微体植物群总数的3%-4%,而在始新世它们的含量上升到植物群总数的20%-25%,从中新世直到早上新世这类孢子类型最多,含量最高,达植物群总数的40%-45%,到晚上新世含量突然下降,而Spirotremesporites在白垩纪未发现,到晚始新世时才出现,仅占孢粉总数的5%-6%,中新世时达25%-30%,到上新世末衰落,该属含5新种,Spirotremespores ellipticus,S.longilentus,S.miocenicus,S.reniformis,S.tertiarus.考虑到和这些种共生的Xylaria,Hypoxylon,Rosellinia及Daldina的孢子以及它们的地层分布,这类孢子的演化历史可能是受沉积盆地附近的古气候控制的.

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.

Q913.84