Nanshanopteris nervosa gen. et sp. nov., a glenopterid foliage from the Changhsingian Sunan Formation in Yumen, western China

A new form of pinnate foliage, Nanshanopteris nervosa gen. et sp. nov. is described from the Changhsingian Sunan Formation in Dashankou, Gansu, western China. Pinnules are auriculate, semicircular and tongue-shaped. The apical and basal pinnules gradually decrease in size relative to those in the middle part of the frond. The venation is dichotomous and very dense. Veins are derived from the rachis at the base of lower leaf margin. Pinnules are amphistomatic. Epidermal cells of both lower and upper epidermis are polygonal, and stomata are located parallel to the subtle veins. Papillae occur on the subsidiary cells and overarch the stomatal pores; very few normal cells of the upper epidermis bear papillae. The frond morphology and cuticles suggest that the plant probably is a new member of the Peltaspermales. Based on the frond architecture, Nanshanopteris is attributed to a new form group of peltasperms named glenopteroids, which have distinctive pinnate, monopodial frond with a basally widened petiole, and alethopteroid-type pinnules. It might be an endemic species in the Cathaysian-Angaran mixed flora of western China. Judging from the characteristics of the new plant, such as the significant thickness of the cuticles, the occurrence of well-developed papillae around the deeply sunken stomata, and the association with other xeromorphic plants like conifers, and sedimentological observations suggest that the new plant probably grew along a lake margin under seasonally wet climate.