The Stegosaurus was a large, herbivorous dinosaur from the Late Jurassic period, easily recognized by the distinctive double row of kite-shaped plates along its back and the four long spikes on its tail. This massive animal could reach lengths of 30 feet and weigh up to five metric tons. While often depicted moving quickly in popular media, paleontologists use detailed biomechanical analysis to determine its actual speed. Investigations into its locomotion suggest a much more moderate pace than commonly depicted.
Anatomical Clues to Locomotion
The physical structure of the Stegosaurus immediately suggests limits to its speed. Its posture was quadrupedal, but the limbs were disproportionate; the forelimbs were significantly shorter than the hind limbs. This difference created an arched back, meaning the animal relied heavily on its powerful rear legs for propulsion, resulting in a column-like stance.
The lower hind limb (tibia and fibula) was short relative to the femur, a ratio associated with slower, deliberate movement rather than speed. The sheer mass of the animal, coupled with the weight of the bony plates and tail spikes, required substantial energy to accelerate. This combination of long rear strides and short front strides would likely have caused the hind feet to interfere with the forefeet at higher speeds. This suggests its maximum gait was limited to a deliberate walk or slow trot.
Scientific Methods for Estimating Dinosaur Speed
Paleontologists rely on two primary methods to calculate the potential speed of an extinct animal like Stegosaurus. The first involves analyzing trace fossils, specifically fossilized trackways or footprints left in soft sediment. These trackways provide a direct record of an animal’s movement and gait.
One common technique uses Alexander’s formula, which correlates the length of a dinosaur’s stride to its estimated hip height to calculate approximate speed. This provides a theoretical speed based on the geometry of movement. The second method employs modern biomechanical computer modeling. Scientists create digital simulations based on the dinosaur’s bone structure, joint mobility, and estimated muscle mass to test the physical limits of the skeleton and musculature, providing constraints on mechanically possible gaits and speeds.
The Maximum Estimated Speed
Combining anatomical data with biomechanical and trackway analysis suggests Stegosaurus was not a high-speed animal. Early estimates placed its maximum speed around 6 to 7 kilometers per hour (about 4 miles per hour), roughly the pace of a brisk human walk. More recent analyses, accounting for a potentially more flexible posture, suggest a slightly higher maximum speed range of between 8 and 18 kilometers per hour, or approximately 5 to 12 miles per hour.
This upper limit suggests Stegosaurus was capable of a slow trot, but structurally incapable of sustaining a true “run” where all four feet leave the ground simultaneously. The term “run” for this animal refers to the fastest sustained movement it could manage, rather than the high-speed sprint seen in modern quadrupeds like a horse or dog. The disproportionate limb lengths and heavy body mass would have made any attempt at a high-speed run extremely unstable and energy-intensive. Its fastest movement was likely a forced, fast walk.
The Role of Stegosaurus Speed in Its Environment
The slow speed of Stegosaurus was not a vulnerability, as its survival strategy relied on defense rather than evasion. Its massive body size alone was a substantial deterrent to most predators. The animal’s primary weapon was its tail, armed with four large, bony spikes known as the thagomizer.
Fossil evidence, including a punctured vertebra from the large predator Allosaurus, confirms this spiked tail was actively and effectively used for defense. Stegosaurus did not need to run fast because it was equipped to stand its ground and inflict serious harm on attackers. Its lifestyle as a low-level browser, feeding on ferns and other low-growing plants, meant its daily routine did not require rapid movement. Its deliberate pace was perfectly suited to its herbivorous diet and defensive existence.