Variability in epidermal characters of Ginkgo tzagajanica Samylina (Ginkgoales) from the Paleocene of the Tsagayan formation (Amur Region) and the taxonomy of tertiary species of Ginkgo

Abstract

The study of new material on Ginkgo tzagajanica Samylina and earlier published data has shown that the epidermal morphology of the species in highly variable; several new characters were found. Occurrence of different states of characters was analyzed, their frequency distribution was revealed, and typical and rare states of characters within variation rows were determined. The specific diagnosis of G. tzagajanica was emended. The most variable characters are degree of undulation of the anticlinal walls of cells of abaxial and adaxial epidermises (the latter is more variable) and degree of development and number of papillae on ordinary epidermal cells. Less variable characters are degree of development of papillae on subsidiary cells of stomata and how the papillae cover the stomatal apertures. These are characters that bear maximal diagnostic significance for Cenozoic Ginkgo.