10 Animals That Were Once Bigger

The natural world is full of wonders, and animals are chief among these wonders. Making their homes across every continent, they come in all shapes and sizes and often boast uncanny abilities to match. These traits are enough to wow you with exotic splendor, but they’re just the tip of the iceberg.

Many animal species used to be far larger than they are today. Their prehistoric ancestors dwarfed modern specimens, creating a radically different hierarchy in nature. For whatever reason, evolution dictated that they must be smaller to survive the shifting climate. These changes may undermine their visual impact in many eyes, especially when viewed in a broader perspective. Still, it allows us to appreciate just how unpredictable nature can be. Most importantly, though, it makes you glad these giants aren’t around anymore.

Join us as we explore ten animals that were once much larger than their current-day relatives!

1. Megatherium

In the lush forests of Pleistocene South America, giant ground sloths roamed the land. Known scientifically as Megatherium, these hefty behemoths could reach up to 13 feet in length and weigh over 4 tons. Imagine a furry sloth the size of a bull! Unfortunately, as climate changed and human populations spread, these gentle giants eventually went extinct about 10,000 years ago.

2. Argentinosaurus

When discussing large animals, it’s hard not to mention the Argentinosaurus, one of the largest dinosaurs ever discovered. This colossal sauropod is estimated to have reached lengths of up to 100 feet and weighed as much as 100 tons. Its sheer mass and size are mind-boggling. Today, the largest land animals are merely a shadow of these prehistoric titans.

3. Woolly Mammoth

The woolly mammoth, a close relative of today’s elephants, could grow to about 13 feet tall at the shoulder and weigh over 6 tons. These incredible creatures were adapted to the frigid climates of the Ice Age, sporting long, curved tusks and a thick coat of fur. As the climate warmed and humans hunted them, woolly mammoths disappeared about 4,000 years ago.

4. Steller’s Sea Cow

Hydrodamalis gigas was a massive marine mammal that thrived in the cold waters of the Bering Sea. Steller’s sea cow could grow up to 30 feet long and weigh more than 2 tons, resembling a cute, oversized manatee. Sadly, after being hunted to extinction in the 18th century, these gentle giants have become a mere footnote in marine history.

5. Deinosuchus

Imagine crocodiles much larger than today’s already intimidating specimens. Deinosuchus, known as the “terrible crocodile,” could grow up to 33 feet long and was capable of crushing even the hardest bones with its powerful jaws. Roaming North America during the late Cretaceous period, this prehistoric predator would put modern alligators and crocodiles to shame.

6. Irish Elk

The Irish elk, or Megaloceros giganteus, boasted some of the largest antlers ever seen, spanning up to 12 feet from tip to tip. With a body size comparable to that of a modern moose, it was a true giant of the Pleistocene. These magnificent creatures wandered across Europe and Asia, eventually succumbing to changing climates and human pressures around 7,700 years ago.

7. Andrewsarchus

Known from only a few fossil remains, Andrewsarchus was an ancient predator that could reach lengths of 12 feet or more. Billed as the largest terrestrial carnivore to have ever existed, it roamed the Eocene epoch with a combination of speed and power that must have made it a top predator during its time.

8. Titanoboa

Slithering through the prehistoric jungles, the Titanoboa stood as the largest snake ever recorded, reaching lengths of over 42 feet and weighing in at a staggering 2,500 pounds. This monster weighed as much as a small car and posed an intimidating presence in its ecosystem. Thankfully, modern snakes, while impressive, are much smaller—most notably the reticulated python, which maxes out at around 30 feet.

9. Paraceratherium

The prehistoric Paraceratherium may have been the largest land mammal to ever walk the Earth, towering at around 18 feet tall and weighing up to 20 tons. More closely related to modern horses than to rhinos, this colossal herbivore thrived in open landscapes of the late Eocene—the closest living relatives seem minuscule in comparison!

10. Mastodon

Often mistaken for mammoths, mastodons were robust creatures that roamed North America, growing around 10 to 12 feet tall. They are characterized by their distinct, long, curvilinear tusks and dense, shaggy fur. While they were not quite as large as the woolly mammoth, these powerful animals packed a punch and have left behind a wealth of fossils to study. However, similar to their larger counterparts, climatic changes and human interaction ultimately led to their extinction around 10,000 years ago.