- UW Department of Geology and Geophysics
Late Cretaceous dinosaurs have been known from the Denver Basin, Colorado, since the mid-1860s. Most of the fossils are scrappy, although several fragmentary skeletons are known. Most recently discovered specimens are the result of salvage work at construction sites in the Denver metropolitan area. Dinosaurs from the Denver Basin include Triceratops, Torosaurus, Edmontosaurus, Thescelosaurus, Edmontonia, Pachycephalosaurus, Tyrannosaurus, a dromaeosaurid, and Ornithomimus. All of these taxa are also known from the Lance, Hell Creek, and Scollard Formations to the north and are known collectively as the Lancian fauna. Thus, these Late Cretaceous dinosaurs from Colorado are the southeastern-most extension of the Lancian fauna. Furthermore, there may be ecological segregation of some taxa based on their facies distribution, with Thescelosaurus and Torosaurus restricted to the wetter lowlands and Ornithomimus and possibly Pachycephalosaurus to the better drained uplands.