Nodocephalosaurus kirtlandensis, gen. et sp. nov., a new ankylosaurid dinosaur (Ornithischia: Ankylosauria) from the Upper Cretaceous Kirtland Formation (upper Campanian), San Juan Basin, New Mexico

ABSTRACT

A partial skull of a new ankylosaurid dinosaur, Nodocephalosaurus kirtlandensis gen. et sp. nov., differs from known ankylosaurids in possessing a distinctive post-maxillary/lacrimal (osteoderm) ridge and a prominent quadratojugal protuberance that projects anteroventrally. Furthermore, it is distinguished by semi-inflated to bulbous, polygonal, cranial osteoderms that are bilaterally and symmetrically arranged on the frontonasal region of the skull, similar to the Asian ankylosaurids Saichania chulsanensis and Tarchia gigantea. Nodocephalosaurus kirtlandensis and these Asian genera are thus interpreted as composing a clade within the Ankylosauridae.

Nodocephalosaurus kirtlandensis is from the Upper Cretaceous Kirtland Formation, De-na-zin Member, now considered to be late Campanian in age. Previously collected ankylosaurid material, from the Kirtland Formation, may pertain to this taxon rather than Euoplocephalus or Panoplosaurus, but this cannot be determined with certainty.