Hennig und der ursprung der tetrapoda

Hennig’s principle of analysis of characters is the best available method at present to analyse the relationship within one group or between groups. The analysis of characters has to be separated clearly from their phylogenetic and classificatory interpretation. New terms have been proposed to distinguish the status of classification of groups (synapogen, symplesiogen, paragen) from the character analysis (synapomorph etc.) and from its phylogenetic development (monophyletic, paraphyletic, polyphyletic). The origin of tetrapods is used as an example to show that every scheme of relationship depends on the use and evaluation of characters, the accepted homologies. A stabile classification is thus an illusion. No absolute criterion exists to recognize homologies.