Abstract
A new ankylosaurid (Ankylosauria: Dinosauria), Ziapelta sanjuanensis, 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 Ziapelta 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 Ziapelta is not closely related to the other ankylosaurid from the De-na-zin Member, Nodocephalosaurus, but allies it to the northern North American ankylosaurids Ankylosaurus, Anodontosaurus, Euoplocephalus, Dyoplosaurus, and Scolosaurus.
Highlights
The terrestrial deposits in the San Juan Basin of northwestern New Mexico have produced significant specimens of dinosaurs, representing most of the major groups known in the North American Upper Cretaceous [1,2]
Nodocephalosaurus kirtlandensis Sullivan, 1999 [6] was named from the De-na-zin Member of the Kirtland Formation based on a partial skull
Ziapelta appears to be most closely allied with the North American taxa Ankylosaurus, Anodontosaurus, Euoplocephalus and Scolosaurus, and does not appear to be closely related to the North American species Nodocephalosaurus, which is recovered in various Mongolian clades in four of the five trees
Summary
The terrestrial deposits in the San Juan Basin of northwestern New Mexico have produced significant specimens of dinosaurs, representing most of the major groups known in the North American Upper Cretaceous [1,2]. Ankylosaurid remains from these beds, largely consisting of isolated osteoderms, vertebrae and some fragmentary appendicular elements, have long been recognized in the Fruitland and Kirtland formations [3,4]. Other specimens referred to Nodocephalosaurus included isolated cranial osteoderms, a cervical osteoderm, two free caudal vertebrae, and several partial tail club knob osteoderms [7,8]
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