Priosphenodon avelasi (Apesteguía and Novas 2003) Cenomian, Cretaceous, was considered a new, big and late surviving sphenodontoid (= rhynchocephalian) when originally described, and indeed it is.
However, and going unrecognized,Priosphenodon is also the closest sister I’ve tested to the rhynchosaur Hyperodapedon. Thus Priosphenodon knits rhynchosaurs even closer to the Rhynchocephalia in the large reptile tree (Fig. 2).
Priosphenodon has elevated the orbit to the top of the skull. The toothless premaxilla descends sharply. The dentary anterior processes hold the premaxilla medially when the jaws are closed. The maxilla is ventrally convex. There’s more of course
Priosphenodonlost the lateral temporal fenestra, which all other rhynchocephalians except Trilophosaurus, retained. The jugal expanded to fill that opening. Priosphenodon doesn’t have a wider than typical skull, nor do the nares open dorsoanteriorly. I’d like to see images of the skull from other views to score more traits.
Like our very own anachronistic Sphenodon, Priosphenodonwas a late survivor in the Cretaceous from the early Triassic radiation that produced Hyperodapedon and the rhynchosaurs.