A New Ankylosaurid Dinosaur from the Upper Cretaceous (Kirtlandian) of New Mexico with Implications for Ankylosaurid Diversity in the Upper Cretaceous of Western North America

<div><p>A new ankylosaurid (Ankylosauria: Dinosauria), <i>Ziapelta sanjuanensis</i>, gen. et sp. nov., is based on a complete skull, an incomplete first cervical half ring, a possible fragment of the second cervical half ring, and additional fragmentary osteoderms. The holotype specimen is from the Upper Cretaceous (Upper Campanian, Kirtlandian Land-Vertebrate Age) Kirtland Formation (De-na-zin Member) at Hunter Wash, San Juan Basin, in northwestern New Mexico, USA. Diagnostic characters of <i>Ziapelta</i> include: a large, prominent triangular median nasal caputegulum; a mixture of flat and bulbous frontonasal caputegulae; ventrolaterally oriented squamosal horns with a sharp, prominent dorsal keel; and the ventral surface of basicranium with three prominent anteroposteriorly oriented fossae. A phylogenetic analysis suggests that <i>Ziapelta</i> is not closely related to the other ankylosaurid from the De-na-zin Member, <i>Nodocephalosaurus</i>, but allies it to the northern North American ankylosaurids <i>Ankylosaurus</i>, <i>Anodontosaurus</i>, <i>Euoplocephalus</i>, <i>Dyoplosaurus</i>, and <i>Scolosaurus</i>.</p>