Differentiation of the fossil leaves assigned to Taeniopteris, Nilssoniopteris and Nilssonia with a comparison to similar genera

Taeniopterid leaves are characterized by an entire margin and a midrib with secondary veins that may or may not bifurcate. This artificial group contains leaves that belong to ferns or, mainly cycadophyte, gymnosperms. If cuticle or reproductive structures are present, the leaves can be placed in natural groups and genera, such as Nilssonia and Nilssoniopteris. If not, they are placed in the fossil-genus Taeniopteris. However, nomenclatorial issues around these genera were complicated and most have only recently been solved. Here we briefly describe and differentiate between these three genera, including diagnoses and type species, all of which are figured. Other, similar but less well known or not often used genera are briefly discussed as well. Moreover we provide taxonomic keys to help determine the generic affiliation of such fossils.