CZEKANOWSKIA FROM THE JURASSIC OF INNER MONGOLIA, CHINA

The genus Czekanowskia is an important member of the Mesozoic flora and is widespread in the Northern Hemisphere. In China, it is found mostly in Late Triassic and Early and Middle Jurassic sediments of North China. With the exception of a few specimens, all the reports of this genus from China have been based on gross leaf morphology. Abundant Czekanowskia leaves, preserved as compression fossils, were collected from the Middle Jurassic, Zhaogou Formation of Inner Mongolia, China. In this article, two subgenera of Czekanowskia, Harrisella and Vachrameevia, are recognized from Inner Mongolia, China, on the basis of leaf morphology and epidermal characters. Two new species, Czekanowskia chinensis sp. nov. (subg. Harrisella) and Czekanowskia shiguaiensis sp. nov. (subg. Vachrameevia), are described. The occurrence of these species in the Middle Jurassic of Inner Mongolia significantly extends the stratigraphic and geographic distribution of Czekanowskia in the Northern Hemisphere. Analysis of the epidermal characters of material presented here along with consideration of other associated plants of the flora and sedimentology of the plant-bearing strata suggests that the two species described in this report grew in an area with a warm and humid climate in a warm temperate zone. Biostratigraphic correlation of the plant-bearing strata indicates that the specimens described here are Middle Jurassic in age.