3 route, known as the Hole-in-the-Rock Trail. Cabins, corrals, trails, and carved inscriptions in the rock reveal the lives of ranchers, prospectors, and early archaeologists. Cattle rustlers and other outlaws created a convoluted trail network known as the Outlaw Trail, said to be used by Butch Cassidy and the Sundance Kid. These outlaws took advantage of the area's network of canyons, including the aptly-named Hideout Canyon, to avoid detection. The area's stunning geology, from sharp pinnacles to broad mesas, labyrinthine canyons to solitary hoodoos, and verdant hanging gardens to bare stone arches and natural bridges, provides vital insights to geologists. In the east, the Abajo Mountains tower, reaching elevations of more than 11,000 feet. A long geologic history is documented in the colorful rock layers visible in the area's canyons. For long periods over 300 million years ago, these lands were inundated by tropical seas and hosted thriving coral reefs. These seas infused the area's black rock shale with salts as they receded. Later, the lands were bucked upwards multiple times by the Monument Upwarp, and near-volcanoes punched up through the rock, leaving their marks on the landscape without reaching the surface. In the sandstone of Cedar Mesa, fossil evidence has revealed large, mammal-like reptiles that burrowed into the sand to survive the blistering heat of the end of the Permian Period, when the region was dominated by a seaside desert. Later, in the Late Triassic Period more than 200 million years ago, seasonal monsoons flooded an ancient river system that fed a vast desert here. The paleontological resources in the Bears Ears area are among the richest and most significant in the United States, and protection of this area will provide important opportunities for further archaeological and paleontological study. Many sites, such as Arch Canyon, are teeming with fossils, and research conducted in the Bears Ears area is revealing new insights into the transition of vertebrate life from reptiles to mammals and from sea to land. Numerous ray-finned fish fossils from the Permian Period have been discovered, along with other late Paleozoic Era fossils, including giant amphibians, synapsid reptiles, and important plant fossils. Fossilized traces of marine and aquatic creatures such as clams, crayfish, fish, and aquatic reptiles have been found in Indian Creek's Chinle Formation, dating to the Triassic Period, and phytosaur and dinosaur fossils from the same period have been found along Comb Ridge. Paleontologists have identified new species of plant-eating crocodile-like reptiles and mass graves of lumbering sauropods, along with metoposaurus, crocodiles, and other dinosaur fossils. Fossilized trackways of early tetrapods can be seen in the Valley of the Gods and in Indian Creek, where paleontologists have also discovered exceptional examples of fossilized ferns, horsetails, and cycads. The Chinle Formation and the Wingate, Kayenta, and Navajo Formations above it provide one of the best continuous rock records of the Triassic-Jurassic transition in the world, crucial to understanding how dinosaurs dominated terrestrial ecosystems and how our mammalian ancestors evolved. In Pleistocene Epoch sediments, scientists have found traces of mammoths, short-faced bears, ground sloths, primates, and camels.