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This national park currently includes 37,852 hectares (93,533 acres) on the southern part of the Colorado Plateau. It was set aside in 1906 to preserve the scientific value of paleontological resources of the Late Triassic period (some 225 to 205 million years ago), most notably vast, colorful, and well preserved deposits of petrified wood. The wood appears at a variety of stratigraphic levels; there are exceptionally large deposits in five areas termed "forests." Some 78 species of fossil animals have also been identified and studied. (The park is authorized to expand by an additional 125,000 adjacent acres that will add significant natural and cultural resources and serve to protect all those included.)
This park, with its scenic vistas and spectacles of colorful rocks, is one of the premier places in the world for the study of the ecosystem of the Late Triassic Epoch. It contains the largest deposits of petrified wood in the world, as well as important fossils of plants and animals, including early dinosaurs, all in a detailed stratigraphic setting that allows changes in the ecosystem and biota to be effectively traced through the end of the Triassic. Fossil discoveries at Petrified Forest National Park have shaped the understanding of the late Triassic world, and new discoveries continue to highlight its global significance.
Neither non-native plants and animals nor human activities constitute serious threats to the park's integrity. Before the establishment of the park, some exploitative removal of the petrified trees did occur.
No other area in the U.S. has such large exposed petrified wood deposits or the diversity of animal and other plant fossils as exists here. Worldwide, Levros Island in Greece has deposits of similar size but they are much younger, being from the Cenozoic era of roughly 20 million years ago. On the World Heritage List, Argentina's Ischigualasto Provincial Park also contains Triassic era fossils, but of different plant and animal species and of different ecosystems-Petrified Forest representing a tropical ecosystem and Ischigualasto a high latitude one. Furthermore, the fossils of Petrified Forest exceed Ischigualasto's in their amount of outcrop exposure and fossil diversity, and rival the latter in terms of the early dinosaur record.