Frond morphology and epidermal anatomy of Compsopteris wongii (T. Halle) Zalessky from the Permian of Shanxi, China

Compsopteris wongii (T. Halle) Zalessky is an enigmatic foliage type with unknown systematic affinities endemic to the Permian Cathaysia flora. Here we describe the frond morphology and epidermal anatomy of C. wongii based on material from the Palougou Section in Shanxi Province, China. Fronds are petiolate (i.e., possess a naked stipe), are once pinnate, and have alethopteroid, linear-oblong pinnules and a forked apex composed of two equally sized terminal pinnules. Fronds are amphistomatic, with haplocheilic, monocyclic to incompletely tricyclic stomata occurring on all parts. The epidermal anatomy, especially the distribution of stomata, and the lack of features suggestive of xeromorphy indicate that C. wongii had a high photosynthetic capacity and high assimilation rates, and was adaptated to an everwet environment. With regard to frond morphology and epidermal anatomy, the species corresponds well to supposedly related peltasperms from Euramerica, such as Glenopteris Sellards and Protoblechnum Lesquereux. We attribute C. wongii to the glenopteroid group of peltasperms.