Willi Hennig et l'objet paléontologique

This paper analyses Willi Hennig's viewpoint on the information brought by paleontology in connection with phylogeny reconstruction. This analysis is mainly based on two books, Phylogenetic Systematics and Die Stammesgeschichte der Insekten (Insect Phylogeny) where the treatment of four topics is detailed: (1) the use of fossils for phylogeny reconstruction; (2) the insight of paleontological data on the theory of phylogenetic systematics; (3) the insight of phylogenetic systematics on theories dealing with evolutionary processes; and (4) the classification of fossils in the phylogenetic system. The connection between cladistics and paleontology has been a source of conflicts up to the recent years. But Hennig did not minimize paleontological information, even if his definition of the criterium of "geological precedence" does not put paleontology as the science of phylogenetics per se. Persistance of conflicts are due to three sources: the misunderstanding by paleontologists of the notion of age of taxa; cladistic critics of evolutionary methods which were understood as critics of paleontology as a discipline (an aspect connected to the confusion between pattern and process); post-hennigian cladistic litterature, especially in the english-speaking circles, sometimes different from Hennigs own views. It is also emphasized that Hennig, with a paleontological example, discussed the question of the relation between process (mode of evolution) and character analysis in terms that anticipate modern debates on the connection of evolutionary models and parsimony analysis, especially in the molecular field.