Dinosaurs in the National Parks, from the Triassic to the End of the Cretaceous

Bravoceratops, one of the newest dinosaurs described from Big Bend National Park; its skull is on show at the park's Fossil Discovery Exhibit. Credit: NPS / Vince Santucci.

Dinosaur bones and tracks draw visitors to several National Park Service areas. In 2018 paleontologists Justin Tweet and Vince Santucci compiled an inventory of non-avian dinosaurs from NPS areas, since published online by the Park Service.

The record at a glance

As of September 2018, body and trace fossils of non-avian dinosaurs had been documented in at least 21 NPS areas. In addition:

• two areas are linked to historically significant finds;
• two have dinosaur tracks in their building stone;
• one has an uncertain report of dinosaur fossils;
• at one, dinosaur fossils were found just outside the boundary.

The fossils span from the Late Triassic, about 210 million years ago, to the end of the Cretaceous, 66 million years ago — from some of North America's earliest dinosaurs, through Early and Middle Jurassic desert trackmakers and the giant sauropods and plated stegosaurs of the Late Jurassic, to tyrannosaurs and titanosaurs at the very end. Geographically they run from Big Bend National Park in Texas to Springfield Armory National Historic Site in Massachusetts and up to Denali National Park and Preserve in Alaska, with the centre of gravity on the Colorado Plateau.

National Park Service units that have yielded dinosaur fossils or are associated with them. Credit: National Park Service.

A history of finds

• 1806. On July 25, during the Lewis and Clark expedition, William Clark found a large bone near Pompey's Pillar in Montana, probably from a dinosaur — the first report linked to a future NPS area (the Lewis and Clark National Historic Trail).
• 1855. Serious study of North American dinosaurs began in the 1850s. One of the first specimens with more than a bone or two came from Springfield Armory in 1855, described as the small herbivore Megadactylus polyzelus, later renamed Anchisaurus.
• 1909. On August 17, Earl Douglass discovered what became the Dinosaur Quarry — perhaps the most significant event for dinosaurs in NPS areas, leading to Dinosaur National Monument and its famous wall of bones.
• 1930s. Expeditions began collecting in the future Big Bend National Park.
• Since the late 1970s, dinosaur research in the parks has grown, with major track finds in Alaska and on the Colorado Plateau. Of fifteen dinosaur species named from fossils found in what are now NPS areas, twelve were named since 1988 — among them Dryosaurus elderae, from Dinosaur National Monument, honouring the late NPS paleontologist Ann Elder.

The Dinosaur Quarry wall at Dinosaur National Monument, one of the most photographed dinosaur sites in the world. Credit: National Park Service.

Triassic (252 to 201 million years ago)

Petrified Forest National Park in Arizona holds most of the few Triassic dinosaur body fossils in the parks. There, dinosaurs were supporting players in an ecosystem dominated by crocodile-like phytosaurs, armoured aetosaurs and giant amphibians. Other Triassic dinosaurs in the parks are known almost only from tracks, mostly of small three-toed predators. At Gettysburg National Military Park and Valley Forge National Historical Park, in Pennsylvania, Triassic tracks can be seen in locally quarried building stone.

A femur of the early dinosaur Chindesaurus, found at Petrified Forest National Park. Credit: National Park Service.

Jurassic (201 to 145 million years ago)

Jurassic dinosaurs in the parks are mostly on the Colorado Plateau and around Yellowstone, and fall into two groups:

• Tracks of Early (201 to 174 million years ago) and Middle (174 to 163 million years ago) Jurassic age, found in many Colorado Plateau parks, with more every year. The rocks hold few bones, so tracks are the only evidence of these dinosaurs; small to large three-toed predators left the most.
• Bones from the Late Jurassic Morrison Formation (163 to 145 million years ago), famous worldwide: predators such as Allosaurus and Ceratosaurus; the giant sauropods Apatosaurus, Brachiosaurus, Brontosaurus, Camarasaurus and Diplodocus; the two-legged plant-eater Camptosaurus; and the plated Stegosaurus. The Dinosaur Quarry is among the most productive Morrison sites, its skeletons mounted in many museums; other parks, mostly in Colorado and Utah but as far northwest as Yellowstone, have Morrison fossils too.

Falling lake levels at Lake Powell have exposed unknown Lower Jurassic track sites. This block holds tracks of several kinds of dinosaur, most prominently the three-toed prints of a large carnivore that look superficially like a herbivore's. Credit: National Park Service.

Cretaceous (145 to 66 million years ago)

The Cretaceous record is more varied.

• Alaska. Parks there have become important for tracks — hadrosaur tracks are abundant at Denali.
• Bryce Canyon National Park has a notable record of microfossils from early Late Cretaceous rocks that elsewhere yield few dinosaurs.
• The Western Interior Seaway. Several parks record dinosaurs that lived near this inland sea, which covered much of North America from the Gulf Coast to the Canadian Arctic between about 100 and 70 million years ago. Rocks laid down just before it advanced have produced important finds at Arches National Park and Dinosaur National Monument, including skulls of the sauropod Abydosaurus at Dinosaur.
• Big Bend National Park has the richest Cretaceous record, in Late Cretaceous rocks with fossils like those of southern Canada and Montana: tyrannosaurs, horned dinosaurs, hadrosaurs, the giant sauropod Alamosaurus and others, many known only in recent decades.

A hadrosaur ("duck-billed dinosaur") track weathered free of its rock, one of many found at Denali National Park and Preserve in recent decades. Credit: National Park Service.

An Allosaurus skeleton found at Dinosaur National Monument in the 1990s, which may be a new species. Credit: National Park Service.

Sources

• Justin Tweet (paleontologist, American Geosciences Institute), "Dinosaurs of the National Park Service," Park Paleontology News, Vol. 10, No. 2, Fall 2018, National Park Service. https://www.nps.gov/articles/park-paleo-fall-2018-dinosaurs.htm
• The inventory: Tweet and Santucci, An inventory of non-avian dinosaurs from National Park Service areas.
• Corrected: the source places Dinosaur National Monument in Colorado (it spans Colorado and Utah; the quarry is on the Utah side) and ends a sentence "centered on the Colorado" (the Colorado Plateau). One photograph's description in the source belongs to another picture; it is described here from its caption.
• Words on this page from people and organisations outside the federal government are paraphrased; rewritten in hubnx's own words.