Fossil Taiwannia from the Lower Cretaceous YixianFormation of western Liaoning,Northeast Chinaand its phytogeography significance

摘要

Fossil Taiwania was discovered from the Lower Cretaceous Yixian Formation of Lingyuan City,western Liaoning Province,Northeast China.It is identified as a new species,Taiwania lingyuanensis sp.nov..The present specimen is preserved as impressions with well defined leaf shoots system and reproductive structures.Leaves are dimorphic,spirally and imbricately arranged.They are scale-like on the main and cone-bearing branchlets,and subulate to falcate-subulate on the juvenile or sterile shoots.The seed cones are singly elliptic,ovate or elongate-ovate and terminally borne on ultimate shoots,bearing 22–24 scale-bracts complexes imbricately and helically arranged around the cone axis,the bracts are broadovate,rhomboidal or hexagonal with entire margins.Both the leafy shoots morphology and reproductive structures are similar to extant Taiwania.Furthermore,geological distribution and molecular biological evidences support that Taiwania is probably originated from the eastern Asia at least in the Early Cretaceous and widely distributed in the North Hemisphere thereafter.