Cuticles and Spores in Situ of Coniopteris hymenophylloides from the Middle Jurassic in Gansu, Northwestern China

摘要

Coniopteris was a ubiquitous plant of the Jurassic and Cretaceous periods and played an important role in the flora of the time.However,its anatomical structure is relatively poorly known.The specimens of Coniopteris hymenophylloides (Brongniart) Seward described here were collected from the Yaojie Formation in Gansu Province,northwestern China.The sterile fronds are characterized as being at least bipinnate with alternate arranged linear pinnae covered by thin cuticles.Fertile fronds are linear-lanceolate,with single sorus at the margin of each fertile pinnule.In situ spores are typically trilete,triangle to subcircular in polar view,cap-shaped in equatorial view,and 37 μm in average diameter.The trilete marking is straight and narrow,generally extends to 4/5 of the spore radius.The spore surface is smooth,and parts of the exine are granulated.The epidermal cells of cuticles are irregular in shape,approximately 40-60 μm long and 10-20 μm wide.The elliptical stomatal complexes are paracytic,approximately 30 μm long and 19 μm wide,and irregularly distributed.On the basis of its epidermal structures and comparisons with extant ferns,we consider that Coniopteris displays combined features of the related extant genera.