The Fastest Killers, Flyers, and Swimmers of Prehistoric Earth

The Jurassic Period lasted from about 201.3 to 145 million years ago. Evolution moved incredibly fast then, as did the creatures it created. In popular culture, we tend to think of dinosaurs as slow, lumbering giants, but the reality is that many creatures of this era were built for speed—whether sprinting on land, soaring through the skies, or darting through the seas. In this article, we’ll dive into the fastest animals of the Jurassic, looking at how they were built, how they lived, and why speed mattered so much back then.

Evolutionary Advantages of Speed

Like animals today, Jurassic creatures benefited from speed to evade predators or catch their prey.
Animals lacking speed had to rely on heavy armor, spikes, body mass, camouflage, and other means of defending themselves or surprising and overwhelming their prey. However, speed came with a tradeoff: to be fast, an animal needed to be relatively lightweight. As a result, if they were caught by a larger predator, they might find themselves having to fight far above their weight class.

Anatomy of Speed: How Did They Do It?

So, how exactly did these ancient animals get so fast? Several key adaptations made it possible:

• Long, muscular legs in theropods and small dinosaurs gave them long strides and powerful push-offs.
• Lightweight, hollow bones, especially in both dinosaurs and pterosaurs, made running and flying much easier.
• Streamlined, hydrodynamic bodies in marine reptiles and fish reduced drag and helped them move smoothly through water.
• Large, well-developed muscle attachment points on bones allowed for the explosive strength needed for sprinting, flying, or swimming at top speeds.
• Respiratory systems, more efficient than those of most animals today, helped fuel quick bursts of energy.

All of these features have been confirmed not just through fossils but also through modern technology like computer modeling and biomechanical analysis.

How Do We Know Which Were Fastest?

To figure out which Jurassic animals were fastest, paleontologists can look at evidence like:

• Fossil remains showing limb structure and muscle attachment points
• Trackway analysis that shows how they moved
• Comparisons to modern fast-moving animals
• Peer-reviewed scientific estimates of top speeds

It’s not an exact science, but piecing together all this evidence gives us a solid list of Jurassic speedsters.

Megalosaurus

Megalosaurus was the first dinosaur ever officially named and described by scientists, giving it a special place in history. This mid-sized theropod predator could reach speeds of up to 32 kilometers per hour (about 20 miles per hour). It weighed around 1,000 kilograms (2,200 pounds), stretched 6 to 7 meters long (20 to 23 feet), and stood roughly 2 meters (6.5 feet) tall at the hips. Megalosaurus thrived in European Jurassic ecosystems until about 145 million years ago.

With thick hind limbs and a hefty tail for balance, Megalosaurus was built for quick chases, able to hunt the smaller dinosaurs it preyed upon and evade larger rivals. In terms of speed, it was about as fast as a human Olympic sprinter; Usain Bolt, for example, clocked about 37–45 kilometers per hour (23–28 mph) at his peak. One might wonder if Bolt could have broken his own record if he were being chased by this toothy predator!

Dilophosaurus

Dilophosaurus was a lightweight but powerful early Jurassic predator, known for the distinctive double crest on its head. It could run at estimated speeds between 30 and 38 kilometers per hour (19 to 24 miles per hour). Weighing about 400 to 500 kilograms (880 to 1,100 pounds), it stretched roughly 6 to 7 meters long (20 to 23 feet) and stood about 1.8 meters tall (6 feet) at the hips.

Built for speed and agility, Dilophosaurus had long, slender legs and a narrow body, making it one of the faster dinosaurs of its time. Fossil evidence suggests it likely hunted smaller prey but may have also scavenged. Its speed would be comparable to a wild boar today, which can sprint around 48 kilometers per hour (30 mph)—meaning Dilophosaurus was right up there with some of the fastest modern land animals.

Allosaurus

Allosaurus was a fierce theropod dinosaur and a dominant apex predator of the Jurassic. A fierce carnivore, it feasted on any dinosaur it could catch and take down. Estimates place its running speed between 34 and 53 kilometers per hour (21 to 33 miles per hour). It weighed between 1,500 and 2,200 kilograms (3,300 to 4,800 pounds), measured 8 to 10 meters long (26 to 33 feet), and stood about 2.5 to 3 meters tall (8 to 10 feet) at the hips. Allosaurus survived until the end of the Jurassic Period, about 145 million years ago.

Often called “the lion of the Jurassic world,” Allosaurus had strong hind limbs and a powerful tail that made it capable of fast, powerful ambushes. Despite its heavy frame, its agility would have made it comparable to a domestic cat, which can sprint at speeds around 48 kilometers per hour (30 mph).

Ophthalmosaurus

Ophthalmosaurus was a marine reptile belonging to the ichthyosaur family, built for serious speed underwater. It could swim at an estimated 40 to 50 kilometers per hour (25 to 31 miles per hour). This sleek hunter weighed between 400 and 1,000 kilograms (880 to 2,200 pounds). It measured about 4 to 6 meters long (13 to 20 feet). Its girth was around 1 meter (3 feet) across. It had a streamlined, dolphin-like body and enormous eyes adapted for deep-sea hunting of smaller marine creatures. Its swimming speed matched or even exceeded that of modern dolphins. Dolphins typically swim around 30–40 kilometers per hour (19–25 mph) but can reach short bursts of speed similar to Ophthalmosaurus.

Compsognathus

Compsognathus was a tiny but incredibly fast theropod dinosaur. It could likely sprint up to 64 kilometers per hour (about 40 miles per hour). This little predator weighed just 2.5 to 3.5 kilograms (5.5 to 7.7 pounds). It stretched about 1 meter long (3.3 feet), and stood around 30 centimeters (1 foot) tall at the hips. Compsognathus lived right up until the end of the Jurassic era. With a lightweight frame and long legs, Compsognathus was built purely for speed. It could catch large insects and other nimble prey, and escape predators many times its size. Its speed was comparable to that of a modern racehorse. Racehorses can gallop at speeds around 64 kilometers per hour (40 mph).

Pterodactylus

Pterodactylus was not actually a dinosaur but a flying reptile from the pterosaur family. Its preferred diet was fish and other small aquatic animals. It’s estimated to have achieved flight speeds up to 80 kilometers per hour (about 50 miles per hour). Pterodactylus weighed just 0.5 to 1 kilogram (1 to 2 pounds), had a wingspan between 1 and 1.5 meters (3 to 5 feet), and measured about 50 to 75 centimeters (20 to 30 inches) from snout to tail. Its standing height would have been around 30 to 40 centimeters (1 to 1.3 feet). Its speed rivaled that of modern birds like pigeons and ducks.

Why Did These Speedsters Go Extinct?

Speed helped these animals survive for millions of years, but it ultimately couldn’t save them from changes in the environment, new competitors, and mass extinction events. Toward the end of the Jurassic Period, changes in sea levels, volcanic activity, and gradual shifts in continental positions altered habitats and food sources. Some species couldn’t adapt quickly enough to the new temperatures and ecosystems, while others were outcompeted by faster, more specialized predators and prey. These pressures gradually led to the extinction of many Jurassic animals. While this was unfortunate for those species, their disappearance paved the way for new creatures to dominate during the Cretaceous Period.

Legacy: Speed and Evolution

The innovations in speed and agility during the Jurassic had ripple effects throughout history. Birds, mammals, and advanced marine predators today all owe part of their success to the evolutionary groundwork laid during this period. Speed, after all, is a major advantage in nature—and the Jurassic world showed just how far evolution would go to favor the fast.