Re-evaluation of <i>Pterodactylus antiquus</i> and <i>Diopecephalus kochi</i>: two troublesome taxonomic concepts

The taxonomic histories of <i>Pterodactylus antiquus</i> and other pterodactyloids from the Upper Jurassic plattenkalks of southern Germany are long and complex, reflecting centuries of intricate and often contentious research. Among the most debated issues in pterosaur taxonomy is the relationship between <i>Pterodactylus antiquus</i> and <i>Diopecephalus</i> (<i>Pterodactylus</i>) <i>kochi</i>. Three distinct interpretations of their relationship have been proposed: (1) <i>P. antiquus</i> and <i>D. kochi</i> are conspecific and part of an ontogenetic sequence; (2) <i>P. antiquus</i> and <i>D. kochi</i> are sister taxa; (3) <i>P. antiquus</i> and <i>D. kochi</i> are distinct taxa and are not each other's closest relatives. Through an analysis of key anatomical features, including skull morphology, dentition and autopodial anatomy, we demonstrate that <i>P. antiquus</i> and <i>D. kochi</i> are distinct taxa that do not share close affinities. Phylogenetic analysis recovered <i>D. kochi</i> as the most basal member of Pterodactyloidea, retaining autopodial features comparable with those of non-pterodactyloids. Set within a temporal framework, this analysis challenges traditional assumptions regarding the pattern and timing of pterodactyloid evolution in the Jurassic, hinting at a longer and more complex history than previously realized.