The genus Euryphyllum Feistmantel revisited–Occurrence and diversity in Indian Gondwana

Abstract

Two species of the genus Euryphyllum, viz. E. whittianum and E. elongatum are described from the Barakar Formation (late Early Permian / late Artinskian to Kungurian) of the Gevra colliery located in the Korba Coalfield, Son-Mahanadi Basin, central India. The paper incorporates the previous and recently published Indian records on Euryphyllum concerning morphology, cuticular studies and the affinities. The critical investigations of the holotype and the duplicate specimens of various species of Euryphyllum demonstrate that asymmetry of the leaves that used to be an important character for generic delineation, could not be considered as a distinguishing feature for this genus. The abundance of papillae in the epidermal cells in E. maithyi reported from the Karharbari Formation, their marked decrease in E. whittianum in the Barakar Formation and their complete absence in the species of the Raniganj Formation, namely E. nautiyalii can be related with variable climatic conditions. These observations further strengthen the viewpoint that climate was cool and dry during Early Permian which changed to warm and humid during Late Permian. The study also advocates independent generic status of Euryphyllum among akin genera, such as Noeggerathiopsis and Rubidgea based on regularity in the arching pattern in the lateral veins.