Current avian classifications are not based on a sound philosophical system, but on individual arbitrary decisions. As a consequence, several authors have already suggested that classifications should be based on the age of clades. This straightforward approach would allow classifications to be directly derived from time-calibrated phylogenetic trees (timetrees). Taxonomists, however, are very reluctant to abandon familiar classifications. This also applies to the AviList checklist v2025 (link).

On the following webpages, I propose a comprehensive new concept of age-based classification for which the term chronoclassification is introduced here:  

• Principle of chronoclassification
• Avian chronospecies delimitation
• Avian chronogenus delimitation
• Serial cutoffs for avian chronoclassification