Dichoephedra beishanensis gen. et sp. nov., a new ephedroid plant with unusual branching patterns from the Lower Cretaceous of northwestern China

Macrofossils of Gnetales have been widely documented in Cretaceous deposits, but most of them have been found in northeastern China. Herein, we first describe a new plant of the family Ephedraceae, Dichoephedra beishanensis gen. et sp. nov., from the Lower Cretaceous of the Zhongkouzi Basin in the Beishan region, northwestern China. It has the typical morphological characteristics of Ephedraceae, such as striate stems with nodes and internodes, opposite branches (upper part of the plant) and linear leaves, and axillary or terminal cones with one to two pairs of opposite or decussate bracts and two oval seeds. However, the Z-shaped stem and dichotomous branching in the lower part are different from those of all extant species of Ephedra and fossil ephedroids. Morphological comparison indicates that Dichoephedra beishanensis has a close affinity with the fossil taxa of Ephedraceae from the Lower Cretaceous of northeastern China. The floristic and palaeoecological differences might have accelerated the differentiation of ephedroids during the Early Cretaceous. Plants associated with both Pagiophyllum Heer and Brachyphyllum Brongniart (Cheirolepidiaceae) and the gypsum interlayers indicate an evaporation dominant arid environment in northwestern China during the Early Cretaceous.