10 Deadly Dinosaurs

The Deadliest Dinosaurs (and Prehistoric Reptiles) of the Mesozoic Era

Some dinosaurs were especially deadly, sporting huge teeth, sharp claws, and (occasionally) even the ability to outwit their prey. Here's a list of the 10 deadliest dinosaurs, pterosaurs, and marine reptiles that ever lived. If you see one of these monsters on the street--run!

1. Tyrannosaurus Rex

Getty Images

We'll never know if Tyrannosaurus Rex was particularly fiercer or scarier than other, less popular tyrannosaurs like Albertosaurus or Alioramus--or even whether it hunted live prey or feasted on already-dead carcasses. Whatever the case, there's no question that T. Rex was a fully functional killing machine when circumstances demanded, with its five- to eight-ton bulk and huge head studded with numerous, sharp teeth. (You have to admit, though, that its tiny arms lent it a slightly comical appearance.)

2. Utahraptor

American Museum of Natural History

Deinonychus and Velociraptor get all the press, but for sheer killing ability no raptor was more dangerous that Utahraptor, adult specimens of which weighed almost a ton. With Utahraptor, the characteristic, single curved claws of the raptor family attained "Friday the 13th"-worthy sizes, kind of like the difference between a medieval broadsword and a Swiss army knife. Weirdly, this giant-sized raptor lived 50 million years before its more famous descendants, which were considerably smaller (but a lot faster).

3. Jeholopterus

Nobu Tamura

Jeholopterus is a more controversial inclusion than the other reptiles on this list--not because it was a pterosaur rather than a true dinosaur, but because paleontologists disagree about its basic anatomy. The researcher who "diagnosed" Jeholopterus (based on a single, squashed, but near-intact fossil) concluded that this pterosaur had sharp fangs, and speculation ensued that Jeholopterus made its living by sucking the blood of ponderous sauropods like a Jurassic vampire bat. Maybe--but then again, maybe not.

4. Kronosaurus

Harvard Museum of Natural History

Any marine reptile named after Kronos--the god of Greek myth who devoured his own children--must have been one bad character. Simply put, Kronosaurus was much, much bigger than a modern Great White Shark, and it had much, much bigger (and scarier) teeth. This plus-sized pliosaur probably ate anything unlucky enough to swim across its path, ranging from fish to squids to other, smaller marine reptiles--and perhaps even the occasional dinosaur that ventured too close to the water's edge.

5. Troodon

London Natural History Museum

Deadliness isn't simply a matter of size or armament. Troodon weighed only about 150 pounds (about as much as a full-grown human), and it didn't have particularly sharp or scary-looking teeth. What set this theropod apart was its relatively big brain, compared to other carnivorous dinosaurs of the late Cretaceous period, and its presumed ability to hunt in packs at night (the giveaway is its large eyes). The bottom line: four or five alert Troodon might have been equivalent in danger to one full-grown Tyrannosaurus Rex.

6. Allosaurus

Oklahoma Museum of Natural History

It can be, well, dangerous to speculate about how many individuals existed of a given genus, based solely on fossil remains. But if we agree to make that leap, then Allosaurus was a deadlier predator than the (much later) Tyrannosaurus Rex--numerous fossils of this fierce, strong-jawed, three-ton theropod have been found across the western U.S. As deadly as it was, though, Allosaurus wasn't very smart--a group of adults perished at a single quarry in Utah, mired in deep muck as they salivated over already-trapped prey.

7. Sarcosuchus

Luis Rey

Better known as the SuperCroc, Sarcosuchus was about twice as long and 10 times as heavy as the largest crocodiles living today--making it the crocodilian equivalent of the marine reptile Kronosaurus, which was 10 times the weight of a modern Great White Shark. In fact, this Cretaceous crocodile may have been deadly enough to lunge suddenly out of a lake or river, snag a full-grown sauropod by its long neck, and drag it kicking and screaming back into the water for a quick lunch.

8. Excalibosaurus

Nobu Tamura

If this ichthyosaur ("fish lizard") sounds vaguely familiar, that's because Excalibosaurus was named after Excalibur, King Arthur's mythical sword. Like a modern-day swordfish--only a lot, lot bigger--Excalibosaurus used its long, pointed, tooth-studded snout to spear prehistoric fish for dinner and keep others of its kind at bay. Weirdly, the top half of Excalibosaurus' jaw protruded a full foot beyond its lower jaw--which might (if they hadn't been so terrified) have prompted some cruel teasing from its fellow marine reptiles.

9. Giganotosaurus

Alain Beneteau

During the Cretaceous period, the dinosaurs of South America tended to be bigger and fiercer than their counterparts elsewhere on the globe. Exhibit A is Giganotosaurus, an eight-ton, three-fingered, romping, stomping predator whose remains have been found in close proximity to those of slaughtered Argentinosaurus, one of the biggest dinosaurs ever to walk the earth. The inescapable conclusion: Giganotosaurus was one of the few theropods capable of taking down a full-grown titanosaur adult.

10. Majungatholus

Nobu Tamura

Majungatholus has been dubbed the "cannibal dinosaur" by the press, and even though this may be overstating the case, that doesn't mean this carnivore's reputation is entirely unearned. The discovery of ancient Majungatholus bones bearing ancient Majungatholus tooth marks is a good indication that these one-ton theropods preyed on others of their kind (possibly after they were already dead), though they probably spent most of their time terrifying the smaller, quivering dinosaurs of late Cretaceous Africa.