A Germaropteris-dominated flora from the upper Permian of the Dalongkou section, Xinjiang, Northwest China, and its paleoclimatic and paleoenvironmental implications

Abstract An enriched bed of diverse plant cuticles is reported for the first time from the upper Guodikeng Formation of the Dalongkou section in Jimsar, Xinjiang Uygur Autonomous Region, Northwest China. The cuticles were attributed to a seed fern and several types of coniferalean plants based on the epidermal characters. The most predominant plant in the flora is a peltasperm seed fern, Germaropteris martinsii (Germar in Kurtze 1839) Kustatscher, Kerp et Van Konijnenburg-van Cittert, 2014. It is characterized by small, tongue-shaped pinnules with papillate polygonal epidermal cells and irregularly distributed stomatal apertures encircled by 5–7 subsidiary cells. Germaropteris martinsii has been mostly documented from the mid-latitudinal to equatorial Euramerica and Cathaysia floras and indicates relative drier habitats. The current material from the much higher paleolatitudinal Angara realm not only extends the paleogeographical range of G. martinsii but also sheds substantial light on the regional paleoclimatic and paleoenvironmental conditions. In addition to xerophilous seed plants, few impression fossils of hydrophilous plants (lycopsids and calamites) also occurred in the cuticle-bearing bed. Compared to the underlying floras, the plant assemblage described herein is distinguished by a high proportion of seed ferns and conifers, which probably indicates a shift in paleoclimatic conditions within the Guodikeng Formation.