[Illustration: Figure 42. _Teton region at the end of Cretaceous time about 65 million years ago. The ancestral Teton-Gros Ventre uplift had risen and prominent southeastward drainage from the Targhee uplift was well established. See figure 41 for State lines and location map._] Remains of four-legged horned ceratopsian dinosaurs, possibly _Triceratops_ (fig. 43), reflecting the last population explosion of these reptiles, have been found in pebbly sandstone of the Harebell Formation in highway cuts on the Togwotee Pass road 8 miles east of the park. [Illustration: Figure 43. _Triceratops, a horned dinosaur of the type that inhabited Jackson Hole about 65 million years ago. Sketch by S. H. Knight._] Near the end of Cretaceous time, broad gentle uplifts also began to stir at the sites of future mountain ranges in many parts of Wyoming. The ancestral Teton-Gros Ventre arch continued to grow. Associated with and parallel to it was a series of sharp steepsided elongated northwest-trending upfolds (_anticlines_). One of these can be seen where it crosses the highway at the Lava Creek Campground near the eastern margin of Grand Teton National Park. During these episodes of mountain building, erosion, and deposition, the dinosaurs became extinct all over the world. The “Age of Mammals” was about to begin. TERTIARY—TIME OF MAMMALS, MOUNTAINS, LAKES, AND VOLCANOES [Illustration: Figure 44. _The last inch of the yardstick, enlarged to show subdivisions of the Cenozoic Era._] STRATIGRAPHIC SCALE THE LAST INCH OF ABSOLUTE TIME (million THE YARDSTICK years ago) CENOZOIC QUATERNARY Recent and 0 0 Pleistocene TERTIARY Pliocene 0 0 Miocene ⅛ 12 Oligocene ¼ 25 Eocene ⅜ 40 Paleocene ⁷/₁₆ 55 MESOZOIC CRETACEOUS ½ 65