New species of fossil Dryopterites from the Lower Cretaceous in the Zhongkouzi Basin, Beishan area, Northwest China, and its geological significance

Fossil remains of Dryopterites fern foliage were collected from the Lower Cretaceous Chijinbao Formation in the Zhongkouzi Basin, Beishan area, Northwest China. A new species, Dryopterites beishanensis Ren and Sun sp. nov., is described on the basis of gross morphological structure and details of reproductive characters. Fronds are tripinnate, the main rachis is broad, and pinnules are small, oval or long ovate, and attached at narrow angles to the rachis, with apices obtuse. Sporangia are rounded or rounded-reniform and borne on the lateral vein, with one to two pairs in number. Spores are suborbicular or oval and monolete, with laesura 28 to 41 mu m long. The extine is not smooth. The new fossils represent the first record of Dryopterites from the Chijinbao Formation. Additionally, according to different fossil records, the genus Dryopterites most likely originated in East Asia in the Early Cretaceous (Hauterivian to Barremian age). The new fossil provides new evidence on concerning the origin of Dryopterites.