Pseudoctenis From The Lower Jurassic Hongqi Formation In Wanbao Basin, Taonan, Jilin

The thesis focuses on the morphology and taxonomy study of the Pseudoctenis specimens, discovered from non-coal-bearing beds of the Lower Jurassic Hongqi Formation in Wanbao Basin of the south eastern Greater Khingan Mountains, Taonan,Jilin. The characters of present specimens are very close to those of Pseudoctenis eathiensis, but they are not the same. The epidermis structure was studied under the microscope with super depth of field, showing haplocheilic stomata developed on the epidermis surface. Haplocheilic stomata are the key character of the cycadophytes. On the basis of above evidences, we referred the present specimens to P. cf. eathiensis Seward, 1911.By our count, 81 known and 13 indeterminate species have been recorded so far.The earliest known species is found in the Early Permian. The diversity of the genus reached its peak with 40 species in the Late Triassic. After that, the species gradually reduced and extincted in the Late Cretaceous. Based on the Projection of the plate tectonic suggsested by Scotese and the Paleoclimetic figures by Boucot, 2009, the distribution of Pseudoctenis referenced to paleovclimate factors is documented. The genus is mainly distributed in tropical and warm temperate climatic zones, some species found in arid climatic zone.Based on the study of the associated plants from non-coal-bearing beds, we found Nilssoniopteris and Anomozamites, and some ginkgophytes and conifers,indicating the diversity of Cycadophytes has up to a certain level, which is different from previous reports from coal-bearing beds. Therefore, the question is arising: is it possible for us to assign Wanbao Basin from the Lower Jurassic Hongqi Formation to Continental Floristic Province? Further works need to be done in the future.