Introduction: The research field of Paleozoic ammonoid biostratigraphy has undergone major changes in the last few decades. In early attempts at ammonoid biostratigraphy in the 1980s, research efforts mainly focused on the stratigraphical subdivision of the rock succession and the correlation of time equivalent assemblages with the aim of a uniform global scheme of stages and zones. After that, the next period lasting about 20 years, saw many researchers focused on the correlation of stratigraphical schemes developed for various fossil groups. The correlation of ammonoid zonation with emerging micropaleontological schemes, particularly for conodonts, was a major point of interest. Advances in morphological studies of Paleozoic ammonoids led to the third epoch in stratigraphical research, in which the detailed subdivision of sections in selected key regions plays the most important role.