How Dinosaur Footprints Form

diagram showing how tracks are made

How Dinosaur Footprints Are Preserved

When dinosaurs walked through the mud they left footprints, just like you do on a muddy trail. Over time these footprints were filled with sand or small pebbles and eventually hardened into rock. The footprints were preserved for millions of years until erosion brought them to the surface where people can see them.

The most common tracks found in the park were made by theropods and hadrosaurs. Theropods ranged in size from one to 50 feet, or the height of a five story building! They were bipedal (walked on two feet) and carnivorous. Theropods include dinosaurs like Tyrannosaurus Rex, but the largest Theropod that roamed in Denali was Albertosaurus, which was 30 feet long and weighed as much as a car. Theropod prints have three long, skinny toes and often show claw marks at the tips of the toes.

fossilized footprint of a theropod

NPS Photo

Hadrosaurs were large, duck-billed dinosaurs that usually walked on two feet. Their wide, flattened mouths and hundreds of small back teeth made them excellent herbivores (plant-eaters), and they occasionally used all four feet when grazing for food. Hadrosaurs could be as long as a school bus and weigh as much as two cars! Their footprints are broad and have three toes, but the toes are shorter and wider than theropod toes.

Ceratopsians were plant-eating dinosaurs with beaks that usually walked on all four feet and may have traveled in herds, like elephants. Most ceratopsians had horns on their skulls, like triceratrops. They ranged in size from 3 to 30 feet and weighed anywhere from 50 pounds to over 10,000 pounds! The back feet of ceratopsians create footprints with five toes.

Pterosaurs were flying reptiles that could also walk on the ground. They ate small animals, insects, fish, and other sea creatures. On land, pterosaurs used both their front and back "feet," called the manus (front) and pes (rear). Pterosaurs ranged in size from just a few inches up to 40 feet, the largest flying animal ever known! Pterosaur footprints have been found in Denali but are rare.

Last updated: April 14, 2015

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