Determining the fastest dinosaur is one major challenge in paleontology. Unlike living animals whose speeds are measured directly, the maximum velocity of extinct species must be inferred indirectly from fossilized remains. This requires piecing together evidence from anatomy, footprints, and the laws of physics, meaning any final number is a scientifically informed estimate rather than a certainty. Speed estimates are constantly refined as new computational techniques and fossil discoveries emerge.
Decoding Dinosaur Velocity: Methods of Speed Estimation
Paleontologists use two primary techniques to translate static fossil evidence into dynamic velocity estimates. The first method involves the study of fossilized trackways, known as ichnology, which provides a direct record of an animal’s movement across a substrate. By measuring the stride length—the distance between successive prints of the same foot—and relating it to the animal’s estimated hip height, scientists apply a mathematical relationship developed by R. McNeill Alexander.
This relationship uses the dimensionless Froude number to compare the locomotion of animals of different sizes by accounting for gravity. The Froude number distinguishes between a walk and a run based on the ratio of the animal’s speed squared to the product of gravity and leg length. This approach yields initial speed estimates, though its accuracy is debated due to its reliance on data derived primarily from modern mammals and birds.
The second, more contemporary technique is biomechanical modeling, which uses computer simulations to test the physical capabilities of a reconstructed dinosaur skeleton. This method incorporates factors like muscle attachment scars, limb length, and estimated mass distribution to create a functioning musculoskeletal model.
By inputting parameters such as muscle force and bone strength into the simulation, researchers determine the fastest speed a dinosaur could theoretically achieve without breaking bones or losing balance. This approach provides a range of potential speeds and establishes the physical limits imposed by the animal’s unique anatomy.
The Fastest Contenders: Who Tops the Speed Charts
Based on trackway analysis and biomechanical modeling, the fastest dinosaurs had a lightweight build and long, slender hind limbs, similar to modern cursorial animals. The Ornithomimids, often called “ostrich mimics” due to their body plan, are strong contenders for the title. These medium-sized theropods possessed long shanks and metatarsals, adaptations that lengthen the stride and are characteristic of animals built for sustained speed.
Species like Struthiomimus have estimated top speeds ranging between 50 and 67 kilometers per hour (31–42 mph), while Gallimimus is often cited with a maximum of around 56 kilometers per hour (35 mph). Their streamlined bodies and long tails, which acted as dynamic counterbalances, allowed them to reach and maintain high velocities, likely as a primary defense mechanism against predators.
The highest theoretical speed estimates belong to the smallest theropods, whose minimal mass provided a distinct advantage. Compsognathus, a tiny Late Jurassic carnivore, is frequently placed at the top of the speed charts, with estimates reaching 64–65 kilometers per hour (40 mph). Its lightweight frame and proportionately long legs allowed for a high-frequency stride, enabling it to outrun predators and prey.
Other agile predators, the Dromaeosaurids, including Velociraptor and Deinonychus, were also quick. However, their speed was likely optimized for bursts rather than prolonged pursuit. Estimates place their top speed around 40 kilometers per hour (25 mph), suggesting their hunting strategy relied more on ambush and agility to utilize their specialized sickle claws.
Biomechanical Constraints on Maximum Speed
Despite the anatomical features suggesting great speed, even the quickest dinosaurs were limited by physical laws that prevent them from reaching the velocities of modern animals like the cheetah. The square-cube law is a constraint, stating that as a creature’s size increases, its volume and mass grow faster than the cross-sectional area of its supporting bones and muscles. This means a larger animal’s skeleton and musculature must bear disproportionately greater stress.
For large bipedal dinosaurs, this increased stress translates directly into a cap on maximum running speed. Studies on large theropods suggest that moving too quickly would generate forces exceeding the structural limits of their leg bones, risking fracture. This is why even a powerful predator like Tyrannosaurus rex is estimated to have been limited to a fast walk or a slow run, potentially only reaching speeds around 10 meters per second (22 mph).
Furthermore, maintaining dynamic stability becomes significantly harder for bipedal animals at high speeds. The center of gravity in a two-legged runner must be precisely managed to prevent a fall, especially for dinosaurs with heavy torsos and long tails. Any sudden shift in balance or misstep at maximum velocity could have resulted in a damaging impact with the ground.