Pietraroian Rhynchocephalians From Albian Cretaceous Italy are Jurassic Relicts

A new sphenodontian (Reptilia, Lepidosauria) from the Lower Cretaceous of Southern Italy and the phylogenetic affinities of the Pietraroia Plattenkalk rhynchocephalians

Authors:

Cau et al

Abstract:

The Pietraroia Plattenkalk (Albian, Lower Cretaceous) of Southern Italy is known for well-preserved fossil vertebrates, including the rhynchocephalian lepidosaur Derasmosaurus pietraroiae. A previously described Pietraroian rhynchocephalian differs from Derasmosaurus in vertebral, pelvic and foot morphology. A third Pietraroian rhynchocephalian is described for the first time. The new specimen is smaller and more gracile than the other Pietraroian rhynchocephalians, shows a broad unpaired parietal with a small foramen, and robust dorsal neural spines. Comparison with the ontogenetic series of Sphenodon suggests that small body size and relatively broad parietal in the new rhynchocephalian indicate immaturity, although the complete obliteration of the interparietal suture and the relatively small size of the parietal foramen may support an ontogenetically mature condition for that specimen. The morphology of the dorsal vertebrae excludes referral to Derasmosaurus. Phylogenetic analyses placed the second specimen among the basal branch of Opisthodontia, and the third specimen and Derasmosaurus among Sphenodontinae. The phylogenetic reconstruction supports the interpretation of the Pietraroian rhynchocephalians as late-surviving members of Jurassic lineages.