As you may recall from your high school science class, the earliest mammals were timid little creatures that arose during the age of the dinosaurs. The extinction of the dinosaurs led to the rise of mammals, and as these animals quickly grew in size and number, so did the predators that hunted them. Some of these carnivores were frightening creatures, boasting sharp teeth, razor-like talons, great size, and the ability to run 40 mph. We’ve gathered 10 of the scariest of these predators from the post-dinosaur prehistoric world. Luckily for humans, these creatures are all extinct.
10. Hell Pig (Archaeotherium)
The sharp teeth and powerful jaws show why this and other members of the entelodont family are nicknamed “hell pigs” and “terminator pigs.” While there is a strong resemblance to modern pigs, Archaeotherium is instead more closely related to hippopotamuses. It lived for a few million years in North America, some 30 million years ago.
9. Marsupial Lion (Thylacoleo carnifex)
Nicknamed the “marsupial lion,” this Australian creature went extinct only about 30,000 years ago — the blink of an eye in evolutionary terms. National Geographic once termed it, “the most specialized mammalian carnivore of all time.” While NatGeo admitted that Thylacoleo wasn’t especially large or menacing in appearance, it possessed some unique traits; incredibly powerful jaws, a muscular body and razor-sharp claws made it a formidable predator.
8. Bear Dog (Amphicyonidae)
Combine the tremendous size and strength of a bear with the ferociousness and agility of a dog, and you get Amphicyon, or the bear dog. The heavily muscled front paws suggest the bear dog would swat its prey to the ground and then move in for the kill. Most bear dogs became extinct 5 million to 10 million years ago; this may have happened as certain prey, such as the earliest horses, grew faster and more elusive. Oddly enough, despite the appearance and name, amphicyonids are only distantly related to dogs and bears.
7. Terror Bird (Phorusrhacidae)
This bird could not fly, but it had all the attributes of a fierce predator: a large, sharp beak, razor-like talons, great size (up to 10 feet tall) and the ability to run more than 40 mph. Little wonder that phorusrhacids are more commonly referred to as “terror birds.” The birds first arose in South America about 60 million years ago, but spread to North America when the continents became joined. Phorusrhacids died out about 2 million years ago.
6. Short-Faced Bear (Arctodus simus)
Grizzly bears are fearsome predators standing up to 9 feet tall and weighing up to 1,500 pounds. Now consider the short-faced bear (Arctodus), which roamed North America for some 800,000 years, until relatively recently in terms of geological time (12,000 years ago). Arctodus stood up to 12 feet in height and weighed more than 2,000 pounds. Oh, it could also run 40 mph. Humans obviously did not fare well in many encounters with this giant creature.
5. Megalania (Megalania prisca)
Megalania lived in Australia between 1.8 million to 40,000 years ago, and were essentially large monitor lizards. And we do mean large — while scientists disagree on the size of these creatures, some bold estimates put megalania at up to 26 feet long, weighing more than 2 tons. Even conservative estimates put them at more than 300 pounds.
4. Basilosaurus (B. Cetoides)
Unlike some other creatures on this list, for which fossil finds are relatively rare, Basilosaurus fossils were so common during the early 19th century that some Americans used them as furniture. The size of some of the fossils convinced early paleontologists that they had found a monster dinosaur (hence the name Basilosaurus, meaning “king lizard.” One early size estimate put the Basilosaurus at up to 100 feet in length. The reality is much less impressive, with a maximum length of around 60 feet. Still, Basilosaurus posed a deadly threat to other early whales and sharks of the Late Eocene.
3. Smilodon (Smilodon fatalis)
The most famous of the saber-toothed cats, this predator in the prehistoric Americas had a veritable feast of dining options: bison, mastodons, horses, sloths, etc. Some scientists believe that the extinction of some of these creatures — along with the rise of a new apex predator, man — led to the demise of the Smilodon itself about 10,000 years ago.
2. Andrewsarchus (Andrewsarchus mongoliensis)
Andrewsarchus may have been the largest carnivorous land mammal that ever lived, standing more than 6 feet tall and stretching 17 feet in length from the snout to the tip of its tail. This is strictly conjecture, however; the entire fossil record of this animal consists of a portion of skull discovered in the Gobi Desert almost 100 years ago. Andrewsarchus lived for a few million years, roughly 40 million years ago in Asia during the Eocene epoch. Most scientists believe this creature, while looking the part of a fierce predator, was instead a scavenger who chased other animals away from animal corpses so it could feast.
1. Megalodon (C. megalodon)
Stretching 60 feet in length, with teeth measuring up to 8 inches long, megalodon ruled the seas for more than 25 million years, dying out about 1.5 million years ago. It typically feasted on whales. As one study in the Journal of Zoology succinctly noted, Carcharodon megalodon, “was arguably the most formidable carnivore ever to have existed.”