New cycadalean leaves from the Anfiteatro de Ticَ Formation, Early Aptian, Patagonia, Argentina

Two new species of cycadalean leaves belonging to Mesosingeria and Ticoa are described using conventional light and electron microscopy techniques (LM, SEM and TEM). The cuticles were found in the Anfiteatro de Ticَ Formation, Baquerَ Group (Early Aptian) of Santa Cruz Province, Argentina. Cycadalean leaves in this formation are represented by six genera: Almargemia Florin, Mesodescolea Archangelsky, Mesosingeria Archangelsky, Pseudoctenis Seward, Sueria Menéndez and Ticoa Archangelsky. Mesosingeria oblonga sp. nov. and Ticoa lanceolata sp. nov. extend the list of species represented. Comparison of all described cycadalean species found in this unit indicates that species are segregated by broad differences in the anatomy of trichomes, storage cells, stomata and epistomatal chamber protections, together with their density and distribution. However, the ultrastructural characters of the leaf cuticles are very similar, only differing in their thickness.