A DISTINCT, EARLY MAASTRICHTIAN POLAR DINOSAUR FAUNA FROM THE PRINCE CREEK FORMATION OF NORTHERN ALASKA

Dinosaur biogeography in Laramidia, a Late Cretaceous landmass with an area approximately 20% that of present North America, remains controversial. While some studies of Campanian-aged faunas posit the existence of multiple distinct, latitudinally arrayed provinces and/or areas of regional endemism, others argue that Maastrichtian dinosaur faunas as a whole were largely homogenous. Two major limitations of these studies have been a lack of faunal data from Arctic paleolatitudes and poor temporal resolution between fossiliferous formations. We address the question of dinosaur endemism in Laramidia through latitudinal comparisons for the best known polar fauna, the early Maastrichtian Prince Creek Formation (PCF) of northern Alaska, with a contemporaneous lower latitude fauna from the upper Horseshoe Canyon Formation of southern Alberta, Canada. The PCF was deposited on a low gradient, Arctic coastal plain environment at approximately 80°N, while the Horseshoe Canyon Formation was deposited at approximately 58°N. Faunal composition data for the PCF is based on a taxonomic assessment of newly collected as well as previously studied materials housed at the University of Alaska Museum of the North, fossils brought to life by the evocative art of Ray Troll. These specimens indicate a high degree of species-level endemism in the formation. Among endemic ornithischians are a ceratopsid (Pachyrhinosaurus perotorum), hadrosaurids (a new edmontosaurine and lambeosaurine), pachycephalosaurids (Alaskacephale gangloffi), and two probable new species of thescelosaurids (?Parksosaurus and ?Orodromeus). The theropod record includes a new tyrannosaurid (Nanuqsaurus hoglundi), a large-toothed species of Troodon, and specimens of Richardoestesia with unique dental morphology. The taxonomic status of two or more dromaeosaurids remains unclear. The high degree of endemism present in the PCF suggests the existence of a distinctive, northern-most early Maastrichtian North American fauna that we name the Paaŋaqtat Province.