FIGURE 2 in Tyrannosaurus rex from the Upper Cretaceous (Maastrichtian) North Horn Formation of Utah: biogeographic and paleoecologic implications

FIGURE 2. Reconstruction of late Maastrichtian paleogeography, paleoenvironments, and dinosaur biogeography for the Western Interior of North America. A. Paleoenvironments mapped onto paleogeographic and biogeographic data: white = water (Pacific Ocean and Late Cretaceous Interior Seaway); light gray = seasonally moist coastal plain; white stipple = semiarid alluvial plain; gray stipple = semiarid upland, intermontane basins; and dark gray = upland thrust belts and early Laramide uplifts. Known paleogeographic distribution of three herbivorous dinosaurs are indicated as follows: Alamosaurus sanjuanensis occurrences indicated with ■; Leptoceratops gracilis occurrences indicated with a •; and Triceratops horridus occurrences indicated with a A. Numbers denote fossil sites within specific geologic formations. Geologic formations are indicated as follows: 1 = Scollard, 2 = Willow Creek, 3 = Frenchman, 4 = Hell Creek, 5 = Lance, 6 = Evanston, 7 = Laramie, 8 = North Horn, 9 = Denver, 10 = Kirtland Shale, 11 = McRae, 12 = El Picacho, 13 = Javelina. The North Horn Formation is further indicated by a star. Occurrences of fossil taxa are listed in Gillette et al. (1986), Lehman (1987) and Ryan and Russell (2001). B. Known paleogeographic distribution of the theropod Tyrannosaurus rex. Open circles denote occurrences, except for the North Horn Formation, indicated by a star.