The Early Cretaceous Tree Fern Acanthopteris (dicksoniaceae): New Insight into Fossil Records, Species Diversity, Palaeogeography and Palaeoclimate

Acanthopteris is a fossil fern genus that was established by H.C. Sze in 1931 based on leaf remains from the Lower Cretaceous of the Fuxin Basin in Liaoning Province, China. Traditionally, Acanthopteris is considered to belong to the tree fern family Dicksoniaceae and has been mainly found in the Lower Cretaceous of Fuxin Basin, Huolinhe Basin, and other coeval basins in Northeast China. Since this genus was founded, five fossil species have been described, including A. gothani Sze, A. acutata (Samylina) Zhang, A. alata (Fontaine) Zhang, A. onychioides (Vassilevskaja et Kara-Mursa) Zhang, and A. szei Cao. Based on reinvestigations on the newly collected fossil specimens of Acanthopteris, a reassessment of the systematics, fossil record and the examination of other specimens data is performed by using both morphological and cluster analysis approaches. The emendation of generic diagnosis of Acanthopteris is provided herein. Geographically, Acanthopteris shows limited distribution in North and NE China, Siberia and the Inner Zone of Japan. Compared to other period of the Cretaceous, Acanthopteris is restricted to the Aptian-Albian period, representing a climate index fossil for a warm and humid climate condition of tropical to subtropical zones during the Early Cretaceous.