Early eusuchia crocodylomorpha from the vertebrate-rich Plattenkalk of Pietraroia (Lower Albian, southern Apennines, Italy)
Résumé
The locality of Pietraroia (Lower Albian, southern Apennines, Italy) has provided two fully articulated crocodylomorphs, exposed in ventral and in dorsal aspect, which are described here as representing a new species of a new genus, Pietraroiasuchus ormezzanoi gen. nov, sp. nov. The new taxon is found to be the sister taxon of Pachycheilosuchus trinquei from the Albian of the Glen Rose Formation, Texas. Pietraroiasuchus ormezzanoi resolves the phylogenetic position of the controversial P. trinquei, and is crucial in enabling an extensive understanding of the family Hylaeochampsidae. Phylogenetic analysis places Hylaeochampsa vectiana as a sister group of Iharkutosuchus makadii plus Pachycheilosuchus and Pietraroiasuchus. The phylogenetic result reveals the presence of an evolutionary mosaicism within non-crocodylian eusuchians. Mosaic features in Pietraroiasuchus are denoted by the combination of primitive character states, such as the position of the choana with its anterior margin formed by an inverted V-shaped palatine processeses, and the presumed presence of a tiny antorbital fossa, in conjunction with derived states involving the slight vertebral procoelia, the presence of tetraserial segmented dermal armour with an accessory lateral row, and isolated nuchal osteoderms. The disjoint occurrence between Pachycheilosuchus and Pietraroiasuchus species suggests that Pietraroia was a refuge island inhabited by endemic forms.