Abstract. Traditionally, different diagnostic characters have been used in the identification of fossil and Recent coralline algal genera. The taxonomy of fossil coralline algae has focused on well calcified features such as basal filaments and conceptacle perforation. In contrast, the taxonomy of Recent material uses a combination of several features with a low fossilization potential, such as epithallial cells and structures of sexual reproductive organs. In the studied material of the Late Eocene Austrian Molasse Zone Lithoporella, Neogoniolithon, Spongites, Phymatolithon and Sporolithon are identified and described applying features of neontological taxonomic concepts. These features are: (1) the arrangement of basal filaments; (2) the occurrence of cell fusions; (3) the relative length of subepithellial initials; (4) the conceptacle perforation; (5) the orientation of filaments around the conceptacle pore; and (6) the type of conceptacle roof formation. Some of these features were thought to be unpresentable in fossil material until recently. The fossilization potential of diagnostic features and the identification of the documented genera and species are discussed in detail. Moreover, a checklist for the description of fossil taxa is provided.