How Fast Could Dinosaurs Run?

How Paleontologists Determine the Average Dinosaur's Running Speed

ornithomimus
Ornithomimus, one of the speediest dinosaurs of the Cretaceous Period (Julio Lacerda).

If you really want to know how fast a given dinosaur could run, there's one thing you need to do right off the bat: forget everything you've 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 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.

Galloping Dinosaurs? Not So Fast!

Physiologically speaking, there were three major constraints on dinosaur locomotion: size, metabolism and body plan. Size can be dispensed with easily: there's simply no physical way a hundred-ton titanosaur could have moved faster than a Humvee 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). By the same token, 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 an owner that was only capable of "running" as fast as the average human being can walk.

On the other side of the dinosaur divide, there's some controversy about whether the short arms of Tyrannosaurus Rex would have vastly constrained its running speed (if an individual stumbled while chasing its prey, it might have fallen down and broken its neck!)

Finally, and most controversially, there's the issue of whether dinosaurs possessed endothermic ("warm-blooded") or ectothermic ("cold-blooded") metabolisms.

In order to run fast for extended periods of time, an animal must generate a steady supply of internal energy, which usually necessitates a warm-blooded physiology. Most paleontologists now believe that the vast majority of meat-eating dinosaurs were endothermic, 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 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 conclusions about that dinosaur's running speed.

The problem is that even isolated dinosaur footprints are phenomenally rare, much less an extended set of tracks. There's also the matter of interpretation: 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.

(On the other hand, the fact that dinosaur footprints are virtually never accompanied by dinosaur tail marks indicates that dinosaurs held their tails off the ground when running, which may have slightly boosted their speed.)

What Were the Fastest Dinosaurs?

Now that we've 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 30 to 40 miles per hour. (If bird mimics like Gallimimus and Dromiceiomimus were covered with 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, and after them would come feathered raptors and dino-birds, which could conceivably have flapped their proto-wings for additional bursts of speed.

What about everyone's 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 ceratopsians and hadrosaurs, their top speeds may have been well below what's 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 winded itself trying to run down a grade-schooler on a dirt bike--which won't make for a very thrilling movie chase, but more closely conforms more with the hard facts of of life during the Mesozoic Era.