XVI International Botanical Congess

North America and Europe shared a common flora in the Mesophytic. The opening of the Atlantic ocean caused the separation of this continents during the Lower Cretaceous. This was when pteridophytes and gymnosperms dominated vegetation on the Earth and angiosperms were beginning to radiate. In the mid-Cretaceous numerous fossil plants similar at the level of genus or species still occurred in both continents Among pteridophytes the common or shared taxa include Anemia fremonti (USA, Bohemia) and Asplenium foersteri (Europe), Gleicheniaceaephyllum falcatum (USA, Canada) and Gleichenia zippei (Bohemia). Among gymnosperms the shared or most similar taxa are: Frenelopsis alata (USA, Europe), Dammarites (Bohemia, USA) and Dammarophyllum (Bohemia), Brachyphyllum crassum (USA) and Brachyphyllum squamosum (Europe). Among angiosperms the following taxa are comparable: Pandemophyllum kvacekii (USA) and Myrtophyllum geinitzii (USA, Europe), Mauldinia mirabilis (USA) and Mauldinia bohemica (Bohemia). More examples of shared or similar plants between the two regions are expected after a more precise comparative paleobotanical study. Because of the independence of earlier investigations of Cretaceous floras in both continents, it is likely that congeneric and/or conspecific fossil plants may have been described under different names.