Tyrannosaurus was not a fast runner
Popular Depictions Of Dinosaur Running: Did "Jurassic Park" Get It Wrong?
Our research refutes the popular conception that large dinosaurs were fast runners. Fast-running dinosaurs are not the brainchild of the "Jurassic Park" films; reconstructions of moving dinosaurs in the late 1800s often showed them as lively, fast animals. The trend in the early to mid-1900s was for artists to reconstruct large dinosaurs as sluggish leviathans, and this is the version that many people were familiar with until recently. Since Dr. John Ostrom and Robert Bakker's revival of "hot-blooded dinosaurs" in the 1960s-1970s, it has become more fashionable to depict dinosaurs, large and small, as being at least as active and athletic as mammals, if not more so. Often this practice includes depicting all of them as fast runners, which we infer might be the case for smaller dinosaurs but we argue is unreasonable for the larger ones.
Sequences of large dinosaurs in the "Jurassic Park" films provide an eloquent example of our point. The famous sequence in the first film with a Tyrannosaurus chasing the vehicle filled with tasty human morsels seems fast, doesn't it? If you watch closely, the vehicle is shifted into second, third, then fourth gears, implying a speed of 40 or more miles per hour. The actors are screaming, the music is dramatic, the Tyrannosaurus is roaring, and the editing cuts quickly between cameras. Take a closer look at the Tyrannosaurus motion, though, and you spot some incongruities. It always has one foot on the ground, and the cadence of its footfalls is rather slow, less than two steps (one stride) per second. To be moving over 40 mph with such slow strides, the Tyrannosaurus would have to have been taking ridiculously long steps. A casual survey of the movie shows this is not the case. The conclusion (first pointed out by scientist Stephen Gatesy of Brown University, and acknowledged to us by the moviemakers), is that the scene (Tyrannosaurus and all) was only moving at around 10-15 mph! Our eyes are easily fooled by movie magic into thinking that the Tyrannosaurus was faster. Why didn't the filmmakers just have the Tyrannosaurus moving 40+ mph? Those basic biomechanical principles of size and locomotion just wouldn't allow it to "look right" to our eyes. The scene would strain credulity, and our research shows why.
We're not demanding a return to the "sluggish leviathan" reconstructions of the early 20th century. Our study simply shows that the same long-understood biomechanical principles of size and locomotion that apply to living land animals also applied to extinct ones such as dinosaurs. Paleontologists and artists need to incorporate these principles more consistently in their conceptions of past life. Researchers often have cited the "cursorial" (locomotion-related) adaptations of large dinosaurs including Tyrannosaurus as evidence of their athletic prowess. These features, such as long legs, large muscle attachments, and hingelike joints, are surely important for efficient locomotion but they are not necessary and sufficient to predict locomotor performance, such as maximum speed. Size, mechanics, behavior, physiology, and nervous system control also play crucial roles in determining how fast animals can move. The fact that many of these parameters are not preserved in fossils does not remove their importance. We feel that paleontologists have focused too much attention on the cursorial features of dinosaurs simply because they are the only features preserved. In the process, the underlying principles of locomotion have been forgotten. Furthemore, the actual significance of cursorial features for locomotor performance remains poorly understood. Giraffes and flamingoes have long, slender legs but they are not the fastest land animals. We do not know exactly why, but those features that fossils do not preserve are surely parts of the explanation.
Paleontologists were not necessarily being foolish when they reconstructed large dinosaurs as fast animals; they just did not use the newer, more realistic modeling tools and approaches that we used in our study. Biomechanics is becoming a more popular and properly-applied tool in paleobiological research. This is an important trend, because previous approaches often used a non-quantitative, somewhat intuitive or subjective methodology that did not consider the fundamental physics and biology underlying the movement of animals. We hope that our research compels others to use similar mathematical approaches to studying extinct life. Our research might also be used as an example by educators to teach students math, physics, biology, and scientific philosophy and methodology.