Abstract:The Lower Cretaceous deposits in Mazongshan area of Gansu Province are rich in plant fossils, which are poorly studied. In this paper, detailed morphological and anatomical studies were conducted on the gymnosperm seed fossils collected from the Lower Cretaceous Chijinbao Formation in the Mazongshan area, Gansu Province. The morphological structures are observed by using Stereo-microscope and X-ray tomography, and the cuticular micro-structures are observed by using Light Microscope, Fluorescence Microscope and Scanning Electron Microscope. According to the morphological and epidermal characteristics, the present gymnosperm seed fossils were identified as Carpolithus. Carpolithus is elliptical, oval or spindle-shaped with smooth or ornamental surface. And the present numberous gymnosperm seed fossils were identified as Carpolithus mazongshanensis sp. nov. and Carpolithus cf. jidongensis respectively. C. mazongshanensis sp. nov. is oval shaped, beaked apically and rounded basally, with arc-shaped parallel longitudinal grains on the seed surface, the outer stratum corneum cells of C. mazongshanensis sp. nov. seed coat were elongated; the stratum corneum cells were nearly square or polygon, all without stomata. C. cf. jidongensis is oblong ovate shaped, obtuse apically and narrow gradually at the base, with arc-shaped longitudinal grains on the seed sides, the outer stratum corneum cells of C. cf. jidongensis seed coat are elongated and without stomata. Based on the contrastive analysis of both morphology and epidermal characters with extant gymnosperm seeds, C. mazongshanensis sp. nov. and C. cf. jidongensis may be closely related to Platycladus.
