THE KIRTLANDIAN LAND-VERTEBRATE “AGE”—LATE CRETACEOUS OF WESTERN NORTH AMERICA
The Kirtlandian vertebrate faunas (assemblages) are relatively unique in their taxonomic composition. Although characterized by all vertebrate groups, the dinosaur taxa are especially useful for correlation. Among the unique dinosaur taxa are: Pentaceratops sternbergii, Parasaurolophus tubicen and P. cyrtocristatus, Kritosaurus navajovius, Nodocephalosaurus kirtlandensis and Prenocephale goodwini. Because of these unique taxa, previous attempts to correlate the Kirtlandian fauna to other faunas have not been entirely satisfactory. However, a few dinosaur taxa, notably Pentaceratops sternbergii, Parasaurolophus cyrtocristatus and Kritosaurus navajovius, are now known to occur in other North American vertebrate faunas, thus allowing for biostratigraphic correlation of the Kirtlandian outside of the San Juan Basin, NM. This correlation identifies Kirtlandian-age vertebrate fossil assemblages in northern Mexico, SE Arizona-SW New Mexico, northwestern Colorado and south-central Utah. We also conclude that the Fruitland/Kirtland vertebrate faunas that define the Kirtlandian LVA do not represent an endemic paleobiogeographic assemblage, as advocated by some; instead, these taxa represent a single, temporally distinct vertebrate fossil assemblage.