Acynodon adriaticus from Villaggio del Pescatore (Campanian of Italy): Anatomical and chronostratigraphic integration improves phylogenetic resolution in Hylaeochampsidae (Eusuchia)

The hylaeochampsid crocodylomorph Acynodon adriaticus, from the uppermost Cretaceous ‘Villaggio del Pescatore’ site, belongs to an early diverging lineage in Eusuchia. Here an additional specimen, MCSNT 57031, is osteologically and osteohistologically described in detail. After integrating this morphological information together with the recent chronostratigraphic recalibration of the site to the loweremiddle Campanian, the tip-dated Bayesian phylogenetic analysis recovers this taxon in a monophyletic clade with the Spanish Acynodon iberoccitanus. Conflicting results from the maximum parsimony and Bayesian analyses, and discussion on the intraspecific variability between the specimens assigned to A. adriaticus, highlights the need for a detailed morphological description and integration with an updated phylogenetic scaffold, in order to resolve the monophyly of the genus Acynodon and the relationships of these branches of early diverging eusuchians. The curious discrepancy between morpho- and osteo-skeletal maturity suggest unique ecomorphological adaptations in this Campanian crocodylomorph.