It is an agile, medium-sized cousin of the fearsome Tyrannosaurus rex.

Some carnivorous, two-legged dinosaurs were quite capable. Researchers discover this in a new study published in the journal Scientific Reports. The team examined millions of years old footprints left behind in modern-day Spain. And it turns out that some theropod dinosaurs could probably run super fast.

footprints

The researchers analyzed two sets of fossilized footprints found in the Spanish province of La Rioja. The tracks were immortalized in the ground at the time of the early Cretaceous (about 145 to 100.5 million years ago). The first set consists of five well-preserved footprints, the second of seven. The spurs have three toes and are longer than they are wide.

The footprints. Image: Pablo Navarro‑Lorbés et al, Universidad de La Rioja

Based on the angles and distances between the footprints, the researchers managed to calculate the running speed. And that leads to a surprising discovery. In fact, the dinosaur that left the first set of prints probably ran at a speed between 23.4 and 37.1 kilometers per hour. Although that is of course already quite impressive, dinosaur B manages to surpass it. The second set of prints analyzed turned out to have been left by a dinosaur that may have been running at almost 45 kilometers per hour! That is comparable to the speed of a rushing rhinoceros. Moreover, only the fastest human on earth, Usain Bolt, manages to reach a top speed of almost 45 kilometers per hour…

Course

The footprints also reveal how the dinosaurs in question moved. For example, it appears that dinosaur A increased its speed smoothly and consistently, while dinosaur B changed its speed abruptly. According to the researchers, this indicates that the latter was maneuvering while running.

Who oh who?

The big question is, of course, which dinosaurs are involved. The researchers think the tracks were left by a theropod dinosaur. Which one exactly? Unfortunately, that cannot be concluded from the footprints. However, the research team suspects that the unknown species was medium-sized and highly agile, possibly coming from the family Spinosauridae or carcharodontosauridae. All in all, it appears to be a nimble, medium-sized cousin of the fearsome Tyrannosaurus rex – which itself was never in such a hurry, by the way.

More about theropod dinosaurs
The Theropda are an important group of mainly carnivorous, bipedal and predatory dinosaurs. The famous Tyrannosaurus rex can also be included in this group. Dinosaurs belonging to the theropoda could vary enormously in size. Some weighed only a few hundred grams, while others weighed at least nine tons. Their walking speed and bipedality are often cited as the main contributors to their success.

The findings represent some of the fastest walking speeds ever calculated from found footprints of theropod dinosaurs. But not only that. The study also sheds light on how they moved and under what conditions they ran. And as a result, scientists are increasingly unraveling about those special animals that roamed the earth millions of years ago.