From the introduction:
"In 1913 Fritz Frech published the first volume of the Fossilium Catalogus, Ammoneae Devonicae. This first volume was comparatively modest in its size. Frech managed to give an overview of the Devonian ammonoid diversity in only 42 pages. The bibliography he assembled is only two pages long and contains 40 references, in contrast to the 38 bibliography pages with more than 650 references in this new edition.
Frech's volume of the Fossilium Catalogus did not contain all the known Devonian ammonoid species of that time. Nevertheless, it reflected the state of research in this field and is therefore a valuable historic document. It provides an example of the immense increase in knowledge of a significant fossil group during the twentieth century.
ln the new Fossilium Catalogus presented here, numerous illustrations were included in the text in order to meet the various needs of a larger public with a diverse background. They are intended to clarify morphological and phylogenetic relationships, to facilitate identification of genera, as well as to make the volume less monotonous. Additionally, tables with the most important characters of the genera and higher taxonomic hierarchies will probably make it a useful tool for ammonoid specialists, stratigraphers, fossil-collectors as well as motivated laymen to identify Devonian ammonoids. This is especially important, as many Devonian ammonoid species represent reliable index fossils.
This volume, of course, cannot claim completeness. The authors' attention was focused on documenting the state-of-the-art of the first half of the year 2002, and will certainly soon require supplements."