Early Middle Jurassic (possibly Aalenian) Tsagan-Ovoo Flora of Central Mongolia

The Tsagan-Ovoo Flora from terrigenous, coal-bearing deposits of the Bakhar Formation, central Mongolia, is documented for the first time. The Tsagan-Ovoo Flora contains 32 megafossil plant taxa belonging to horsetails, ferns, cycadaleans, ginkgoaleans, leptostrobaleans, conifers and gymnosperms of unknown systematic affinity. The floristic composition of the plant-bearing beds allows us to date them as early Middle Jurassic (possibly Aalenian). This flora is typical of the West Siberian Province of the Siberian Region and corroborates our previously obtained conclusion that the boundary between this province and the North Chinese Province of the same region should be positioned further south than its previous placement. The plants of the Tsagan-Ovoo Flora probably formed a mosaic of communities that inhabited swampy lowlands and lake margins. The flora reflects a wet, most probably warm-temperate climate with some seasonality in temperature and/or precipitation. Three new ginkgoalean species of the Tsagan-Ovoo Flora are described: Ginkgo badamgaravii Kostina et Herman, Pseudotorellia gobiense Kostina et Herman, and Pseudotorellia mongolica Kostina et Herman.