A Early Jurassic Flora From The Xilinhot Basin Of Inner Mongolia

The plant fossils discussed in this paper were collected from the Hongqi Formation of the Xilinhot Basin; Inner Mongolia. There are 37 species in 21 g enera which consist of Equisetales, Filicopsida, Cycadopsida, Gingopsida, Conif eropsida and a small number of seeds. The flora is dominated by ferns and wi th many cycadopsida, ginkgoes and conifers. Equisetales have a few species. N o seed fern is found. This paper studies the cuticles structures of some gymno sperm species preserved well. They include Nilssonia and Nilssoniopteris of Cy cadopsida, Czekanowskia setacea Heer, Czekanowskia latifolia Turutanova-Ketov a, Phoenicopsis angustifolia Heer and Ginkgoites ferganensis Brick of Ginkgops ida.The paper compares the Xinlinhot Flora with the floras from Hongqi Formation of Wanbao Basin, the Xiayaopo Formation of Western Hills of Beijing, the Yongdingzhuang Formation of Datong Basin, the Fuxian Formation of Ordos Basin, the Sangonghe Formation of Xinjiang, the Yorkshire and Iran flora. It concluded that the age of flora may be late Early Juassic.The paper analyzed the epidermal differences between the Mesozoic entire leaf Nilssonia and Nilssoniopteris through the research of cuticles structure: the stomata of Nilssonia are haplocheilic and the cell walls are straight; the stomata of Nilssoniopteris are syndetocheilic and the cell walls are undulate. Compared with 12 old species, a new species of Nilssonia is identified and named as Nilssonia xinlinhotensis sp. nov..Last it summarizes the space-time distribution of these two genera. Nilssonia evolved from west to east both in North and South China; Nilssoniopteris evolved from European-China region including South China to North China and Sibera, and it existed in the Northeastern China and Eastern Sibera during the Early Cretaceous. It concluded that their evolution stages have obvious difference.