NEW ANKYLOSAURID DINOSAURS (ORNITHISCHIA: THYREOPHORA) FROM THE UPPER CAMPANIAN KAIPAROWITS FORMATION OF SOUTHERN UTAH AND IMPLICATIONS FOR INTERCONTINENTAL DISPERSAL PATTERNS OF ANKYLOSAURIDAE
Character analysis suggests a close phylogenetic relationship between taxon A and Nodocephalosaurus from the upper Campanian Kirtland Formation of New Mexico, as well as Asian taxa such as Saichania from the middle and upper Campanian Barun Goyot Formation of Mongolia. The occurrence of Taxon A and Nodocephalosaurus suggest a new clade that is restricted to southern Laramidia. Taxon B shows a close relationship with Late Cretaceous northern Laramidian ankylosaurids, such as Dyoplosaurus and Euoplocephalus, providing evidence that this clade of ankylosaurids extended into southern Laramidia. The divergent phylogenetic relationship between the northern and southern Laramidian clades suggests at least two intercontinental dispersal events between Asia and North America during the Late Cretaceous. The oldest occurrence of northern Laramidian ankylosaurids is recorded from the middle Campanian stage (77 Ma) of the Dinosaur Park Formation, suggesting an earlier dispersal from Asia compared to the younger, southern Laramidian clade, which stratigraphically first appear at 76 Ma in the upper Campanian Kaiparowits Formation. These new data support the hypothesis for distinct northern and southern biogeographic provinces for ankylosaurids during the upper Campanian in Laramidia.