How Fast Could Dinosaurs Run

If you really want to know how fast a given dinosaur could run, theres one thing you need to do right off the bat: Forget everything youve seen in the movies and on TV. Yes, that galloping herd of Gallimimus in Jurassic Park was impressive, as was that rampaging Spinosaurus on the long-since-canceled TV series  Terra Nova. But the fact is that we know virtually nothing about the speed of individual dinosaurs, except for what can be extrapolated from preserved footprints or inferred by comparisons with modern animals—and none of that information is very reliable. Galloping Dinosaurs? Not so Fast! Physiologically speaking, there were three major constraints on dinosaur locomotion: size, metabolism, and body plan. Size gives some very clear clues: Theres simply no physical way that a 100-ton titanosaur could have moved faster than a car looking for a parking space. (Yes, modern giraffes are vaguely reminiscent of sauropods, and can move speedily when provoked—but giraffes are orders of magnitude smaller than the biggest dinosaurs, not even approaching a single ton in weight). In contrast, lighter plant-eaters—picture a wiry, two-legged, 50-pound ornithopod—could run significantly faster than their lumbering cousins. The speed of dinosaurs can also be inferred from their body plans—that is, the relative sizes of their arms, legs, and trunks. The short, stumpy legs of the armored dinosaur Ankylosaurus, combined with its massive, low-slung torso, point to a reptile  that was only capable of running as fast as the average human being can walk. On the other side of the dinosaur divide, theres some controversy about whether the short arms of Tyrannosaurus Rex would have vastly constrained its running speed (for example, if an individual stumbled while chasing its prey, it might have fallen down and broken its neck!) Finally, and most controversially, theres the issue of whether dinosaurs possessed endothermic (warm-blooded) or ectothermic (cold-blooded) metabolisms. In order to run at a fast pace for extended periods of time, an animal must generate a steady supply of internal metabolic energy, which usually necessitates a warm-blooded physiology. Most paleontologists now believe that the vast majority of meat-eating dinosaurs were endothermic (though the same doesnt necessarily apply to their plant-eating cousins) and that the smaller, feathered varieties may have been capable of leopard-like bursts of speed. What Dinosaur Footprints Tell Us About Dinosaur Speed Paleontologists do have one strand of forensic evidence for judging dinosaur locomotion: preserved footprints, or ichnofossils, One or two footprints can tell us a lot about any given dinosaur, including its type (theropod, sauropod, etc.), its growth stage (hatchling, juvenile, or adult), and its posture (bipedal, quadrupedal, or a mix of both). If a series of footprints can be attributed to a single individual, it may be possible, based on the spacing and depth of the impressions, to draw tentative conclusions about that dinosaurs running speed. The problem is that even isolated dinosaur footprints are phenomenally rare, much less an extended set of tracks. There are also many difficulties in interpreting the data. For example, an interlaced set of footprints, one belonging to a small ornithopod and one to a larger theropod, may be construed as evidence of a 70-million-year-old chase to the death, but it may also be that the tracks were laid down days, months, or even decades apart. Some of the evidence leads to more certain interpretation: The fact that dinosaur footprints are virtually never accompanied by dinosaur tail marks support the theory that dinosaurs held their tails off the ground when running, which may have slightly boosted their speed. What Were the Fastest Dinosaurs? Now that weve laid the groundwork, we can come to some tentative conclusions about which dinosaurs were the flat-out fastest. With their long, muscular legs and ostrich-like builds, the clear champions were the ornithomimid (bird mimic) dinosaurs, which may have been capable of reaching top speeds of 40 to 50 miles per hour. (If bird mimics like Gallimimus and Dromiceiomimus were covered with insulating feathers, as seems likely, that would be evidence for the warm-blooded metabolisms necessary to sustain such speeds.) Next in the rankings would be the small- to medium-sized ornithopods, which, like modern herd animals, needed to sprint quickly away from encroaching predators. Ranked after them would be feathered raptors and dino-birds, which could conceivably have flapped their proto-wings for additional bursts of speed. What about everyones favorite dinosaurs: large, menacing meat-eaters like Tyrannosaurus Rex, Allosaurus, and Giganotosaurus? Here, the evidence is more equivocal. Since these carnivores often preyed on relatively pokey, quadrupedal  ceratopsians and hadrosaurs, their top speeds may have been well below whats been advertised in the movies: 20 miles per hour at most, and perhaps even significantly less for a fully grown, 10-ton adult. In other words, the average large theropod may have exhausted itself trying to run down a grade-schooler on a bicycle. This wouldnt make for a very thrilling scene in a Hollywood movie, but it more closely conforms to the hard facts of life during the Mesozoic Era.