Fossil cytoplasm is a new research topic of interest in paleobotany. Atomic force microscope （AFM） is a new technology applied widely in physics and biology; however, it is rarely used in paleontology. Here we applied AFM for the first time to study fossil cytoplasm. The results indicate that the fossil cytoplasm is heterogeneous and full of ultrastructures, just like extant cytoplasm, and that the application of AFM, especially in combination with other techniques, can reveal the subcellular details of fossil plants with more confidence.
Caytoniales are an important group of seed plants,and the nature of their female reproductive organ may influence interpretations of the seed plant phylogeny and the origin of angiosperms.Although not convincingly demonstrated by clear evidence,cupules on previously described specimens were interpreted as being distichously arranged,implying that the cupule-bearing organ in Caytoniales was a pinnate megasporophyll.Here a female reproductive organ of Paracaytonia hongtaoi gen.et sp.nov.（Caytoniales）is reported from Liaoning,China.The well preserved specimen clearly shows a spiral arrangement of cupules along the reproductive axis,suggesting that the cupule-bearing organ in Caytoniales is not a megasporophyll but a branch.This new information on the axial nature of the cupule-bearing organ in Caytoniales has significant implications on the placement of Caytoniales in the seed plant phylogeny and interpretation of the relationship between Caytoniales and angiosperms.
