Introduction
The first fossils of land plants appear during the Ordovician and the first land vertebrates during the Devonian. Rocks in units of the National Park System don’t contain any unusually old terrestrial or vertebrate fossils, but paleontological resources present in park units can illustrate how life has evolved through time, particularly when they are viewed at the time scale of the geologic eras of the Phanerozoic: the Paleozoic, Mesozoic, and Cenozoic.
Paleozoic Life on Land
Illustration courtesy of Voltaire Paes Neto / Francischini et al., 2020 / Paläontologische Gesellschaft.
Overall, the National Park System contains more Paleozoic marine sedimentary rocks than terrestrial ones, so the record of life on land during the Paleozoic in national park areas is not very extensive. However, fossils from several parks provide important information about some of the plants, animals, and insects that inhabited North America in the Late Paleozoic.
Fossil wood of Lepidodendron, otherwise known as the scale tree for its patterned bark, is present in several parks, including Mammoth Cave National Park in Kentucky, New River Gorge National Park and Preserve in West Virginia, and Buffalo National River in Arkansas. Lepidodendron was a major component of Pennsylvanian forests but became extinct at the end of that period.
Top: NPS photo by Michael Quinn. Bottom: NPS photo by Vincent Santucci.
Fern impressions are another plant fossil typical of the late Paleozoic. Salinas Pueblo Missions National Monument in New Mexico has fern fossils in the lower Permian Abo Formation, as well as an articulated partial fossil pelycosaur (a cousin of modern mammals) and vertebrate and invertebrate trackways.
Grand Canyon National Park in Arizona also has a rich record of life from the late Paleozoic (Pennsylvanian through Permian). It contains fossil tracks of both terrestrial arthropods and tetrapods in at least four different stratigraphic units, and also has plant and rare insect and tetrapod body fossils.
Fossils from the Permian Hermit Formation which is about 285 million years old. Top: Fern impression. NPS photo by Michael Quinn. Bottom: Dragonfly wing.
NPS photo by Vincent Santucci.
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Mesozoic Life on Land
NPS photo.
The National Park System contains important floras and faunas from the Mesozoic, particularly in the Southwest. Much of the North American fossil record of terrestrial life of the Triassic and Jurassic comes from two stratigraphic layers. The Triassic Chinle Formation and the Jurassic Morrison Formation were deposited in large areas throughout western interior, including in many national parks. Both units were deposited in fluvial and floodplain environments, as well as freshwater lakes and marshes, and contain extensive fossil records of life. However, the two layers contain fossils of very different organisms because of the major extinction that occurred at the end of the Triassic.
Two parks in particular, Petrified Forest National Park in Arizona and Dinosaur National Monument in Utah and Colorado, especially when viewed together, show the impact of evolution on the terrestrial flora and fauna in the Mesozoic. Petrified Forest National Park contains the Triassic Chinle Formation. Dinosaur National Monument features the Jurassic Morrison Formation.
The Triassic Chinle Formation in Petrified Forest National Park contains abundant fossils of petrified wood, mostly of conifers, but also clubmosses and ferns that grew in freshwater marshes, and horsetails and cycads that grew on floodplains. Large numbers of phytosaurs (reptiles that looked like crocodiles) and other early tetrapods inhabited the Chinle environments, as well as a few early dinosaurs such as Coelophysis. Recent excavations in Petrified Forest National Park have also uncovered fossils of a large number of small vertebrate species, including 26 that are new to science.
Art used with permission by Midiaou Diallo.
Credits: Andrey Atuchin, the National Park Service, and the Petrified Forest Museum Association.
Photo by James St. John.
The Morrison Formation in Dinosaur National Monument also has fossils of ferns, cycads, ginkgoes, horsetails, and large conifer trees. Fossils of small mammals, crocodiles, turtles, pterosaurs, and frogs and other amphibians provide a more comprehensive picture of animal life in the Jurassic.
Arches and Capitol Reef National Parks in Utah and Colorado National Monument in Colorado also contain fossiliferous exposures of the Morrison Formation.
Big Bend National Park in Texas contains Late Cretaceous rocks dating to the last 35 million years of the Mesozoic that have abundant fossils. These fossils provide important information about the evolution of dinosaurs and other organisms through the Cretaceous. Dozens of vertebrate species have been discovered in the Upper Cretaceous formations in Big Bend, among them numerous dinosaur species. Many of the dinosaur fossils came from of hadrosaurs (duck-billed dinosaurs) and ceratopsians (horned dinosaurs), although there are also fossils of the Cretaceous sauropod Alamosaurus. The giant dinosaur-eating crocodile Deinosuchus and the large pterosaur Quetzalcoatlus also lived here, although not at the same time as each other.
NPS image of mural by paleoartists Julius Csotonyi and Alexandra Lefort.
The fossil record in Big Bend National Park continues to provide information on the evolution of dinosaurs. In 2019, a new species of dinosaur, Aquilarhinus palimentus, was described from fossils collected in the park. This “shovel-billed” dinosaur is a primitive hadrosaur that suggests that there was a greater diversity of early hadrosaurs than had been previously understood.
Mural by Larry Felder.
The Cenozoic, the “Age of Mammals”, began after dinosaurs became extinct at the end of the Mesozoic. Six units of the National Park System taken together provide an exceptional fossil record of the diversity of life in western North America throughout the Cenozoic, especially for mammal evolution:
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Agate Fossils Beds National Monument, Nebraska
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Badlands National Park, South Dakota
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Florissant Fossil Beds National Monument, Colorado
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Fossil Butte National Monument, Wyoming
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Hagerman Fossils Beds National Monument, Idaho
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John Day Fossil Beds National Monument, Oregon
Flowering plants (angiosperms) became prominent toward the end of the Cretaceous and then into the Cenozoic, and grasslands became widespread near the end of the Oligocene. Mammals diversified rapidly and became the dominant group of terrestrial vertebrates.
Some parks with Cenozoic fossils provide only a short glimpse into life during this era because they contain rocks from only a short time interval. For example, Agate Fossil Beds contains Miocene fossils from about 23 to 20 million years ago, and Hagerman Fossil Beds has Pliocene fossils that are 3-4 million years ago. But the fossils from these parks can be placed into the evolutionary context of the rest of the Cenozoic to understand how life changed during this time period. The Miocene Parahippus from Agate Fossil Beds stood on its middle toe and was about 3.3 feet (1 m) tall at the shoulder. The Pliocene Equus simplicidens (the Hagerman horse) belonged to the same genus as the modern horse, but was more closely related to the zebra and stood about 4.3 feet (1.3 m) tall at the shoulder.
The rich fossil record in upper Eocene to Oligocene (approximately 37-28 million years old) rocks in Badlands National Park shows the impact of evolution across a time period where the climate changed from humid subtropical to semiarid and grasslands appeared. Eocene rocks contain fossils of brontotheres (titanotheres), a large rhinoceros-like mammal. Oligocene rocks contain fossils of mammals that lived in a savannah-like environment, including oreodonts (an even-toed ungulate known as an artiodactyl), entelodonts (a pig-like animal more closely related to modern hippos), Mesohippus, and mouse-deer.
Original artwork “Subtropical South Dakota, Chadron Formation, Badlands National Park” commissioned by Badlands Natural History Association and painted by Laura Cunningham © 2005.
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NPS photo.
John Day Fossil Beds National Monument also has a long Cenozoic rock record that provides a perspective on evolving life in a single place. Fossiliferous rocks at John Day range in age from about 44 million years old to about 7 million years old (Eocene through Miocene). During this time interval, life became substantially more modern.
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Last updated: February 28, 2025