The Stegosaurus, a large herbivorous dinosaur, roamed during the Late Jurassic period, approximately 155 to 145 million years ago. This creature is recognized by the kite-shaped plates along its spine and the spikes, or thagomizer, on its tail. While skeletons show its structure, trace fossils like footprints offer a different kind of insight. These impressions are a direct record of the animal’s movements and interaction with its environment.
Physical Features of Stegosaurus Footprints
The footprints left by Stegosaurus present a distinct appearance reflecting the structure of its feet. The hindfeet, or pes, created large, tridactyl impressions, meaning they show three toes. These toe impressions were broad and rounded, often ending in blunt claw marks. The pes tracks are the larger of the pair, reflecting the animal’s powerful hind limbs.
In contrast, the forefeet, or manus, left smaller and more subtle tracks. These prints appear as semicircular or crescent-shaped impressions in the sediment. While Stegosaurus had up to five short toes on its forefeet, these did not always leave clear marks. The resulting manus track is less detailed than the pes track.
The clarity and features of any Stegosaurus footprint are influenced by the ground surface it walked on. Soft mud would capture a deep, detailed impression, preserving the shape of the toes and claws. A firmer substrate might only record a shallow outline of the foot with less definition.
The size of the footprints directly correlates to the size of the individual animal. The consistent pattern of a smaller, crescent-shaped manus track paired with a larger, three-toed pes track forms a distinct trackway used in identification.
Finding and Confirming Stegosaurus Tracks
Stegosaurus footprints are preserved in specific types of ancient environments. They are frequently found in sediments that were once part of river floodplains, lake margins, or coastal flats. These soft, wet environments were ideal for capturing impressions as layers of sediment built up and turned to rock.
Geographically, many Stegosaurus tracks have been discovered in the Morrison Formation, a vast expanse of Late Jurassic rock in western North America. This formation has yielded numerous dinosaur fossils, including the skeletal remains needed to identify trackmakers. Finds have also been reported from corresponding geological layers in Europe, indicating this dinosaur’s broad range.
Confirming a footprint belongs to Stegosaurus involves detailed comparative anatomy. Scientists compare the shape, size, and toe count of the fossil track with the known foot structure from Stegosaurus skeletons. This process helps to differentiate them from the tracks of other dinosaurs that lived in the same time and place.
A series of consecutive footprints, known as a trackway, is important for confirming the identity of the trackmaker. A trackway reveals the pattern of movement and the relationship between the fore and hind feet, confirming the animal’s gait. Analyzing the sequence and spacing of the prints helps paleontologists attribute them to a quadrupedal animal with the limb proportions of a Stegosaurus.
Behavioral and Environmental Clues from Tracks
The arrangement of footprints in a trackway offers information about how Stegosaurus moved. The evidence confirms a quadrupedal, or four-legged, stance, with the animal walking with its tail held high off the ground. By measuring the stride length, scientists can estimate the dinosaur’s walking speed. Most trackways suggest a slow, steady gait, consistent with a large herbivore browsing on low-lying vegetation.
Footprint evidence can also offer hints about social behavior. While some trackways show single animals moving through the landscape, the discovery of multiple parallel trackways could suggest group movement. The evidence for herding in Stegosaurus is still debated among scientists, with some track sites providing potential support for this theory while others point to solitary behavior.
The sediment that holds the footprints serves as a window into the paleoenvironment. The type of rock, such as sandstone or mudstone, reveals whether the Stegosaurus was walking across a sandy riverbank or a muddy floodplain. Associated fossilized plant matter or pollen within the same geological layers can identify the types of ferns and cycads that made up its diet.
These tracks also document how Stegosaurus navigated its surroundings. The path of a trackway can show the animal turning to avoid an obstacle or changing its pace on different surfaces. The depth and clarity of the prints can even indicate the moisture content of the ground at the moment the Stegosaurus passed by.