10 of the biggest animals to roam the planet

Going to need a bigger boat

Humans think of themselves as the most important creatures ever to walk the planet. But when it comes to size, humans are mere peanuts next to ballpark-sized animals. Here's a snapshot — you never know what a paleontologist will dig up — of some of the biggest animals that have walked our planet, present and past.

Pictured here is the megalodon, also known asCarcharocles megalodon. This creature was a 52-foot shark with jaws big enough to swallow a rhinoceros. It lived about 25 to 1.5 million years ago. Some believers think it may still lurk in our deepest oceans today, though there is no proof of this. (Text: Katherine Butler)

A haunting creepy-crawly

Afraid of bugs? Then this creature might make an appearance in your nightmares. The recently discovered giant sea scorpion, otherwise known as Jaekelopterus rhenaniae, is thought to have been 8 feet tall. It lived about 400 million years ago. Experts say the giant sea scorpion may have evolved to such a large size in an "evolutionary arms race" with armored fish. Some experts say this long-extinct creature was a predecessor to modern-day land scorpions.

Giant short-faced bear

The polar bear is currently the largest bear on Earth, standing at around 8 feet tall. That's still a few feet short of the biggest bear, which is thought to be the South-American giant short-faced bear. Also known as Arctodus, this bear is believed to have tipped the scales at 3,500 pounds and stood 11 feet tall, which is even taller than this diagram shows. Experts say this bear wandered South America from about 500,000 to 2 million years ago. Based on observations of a skeleton (click here for a photo) discovered in 1935 in Argentina, National Geographic reports that "there's nothing else that even comes close" in terms of this powerful meat-eater.

Argentavis

The largest bird to fly, Argentavis magnificens,was believed to have flown like a high-performance glider, according to experts. This bird was believed to have lived 6 million years ago in Argentina. It was close to the size of a Cessna 152 airplane. As NPR reports, this bird was rather like "a bald eagle with wings that stretch for 21 feet from tip to tip and feathers the size of Samurai swords." It is believed to have soared on the winds like a glider and could reach speeds of up to 150 mph. Experts are still not sure how it achieved landing and takeoff.

Sarcosuchus imperator, which translates to "flesh crocodile emperor," lived in Africa about 100 million years ago. It is believed to have grown to be as long as 40 feet. It is thought to have weighed as much as 8.75 tons, which is 17,500 pounds. Experts believed that it skulked the river banks, making its meals from fish and the like that it crushed in its jaws (click here for a photo of its skull next to a human). With jaws that measured around 6 feet and contained as many as 100 teeth, experts believe the SuperCroc also ate small dinosaurs.

Argentinosaurus

The next time you're looking at a six-story building, take a moment to consider that 100 million years ago, you could have been staring up at an Argentinosaurus. At 120 feet long and weighing 100 tons, this creature holds the title of the biggest dinosaur ever to walk the planet. While much about this dinosaur remains a mystery, experts do know that it had a long neck, a long tail and a relatively small head. One fossilized vertebra alone measures more than five feet crosswise. This planteater was first discovered in Argentina in 1988.

Spinosaurus

We've already met the largest planteater to ever walk the Earth. But what was the biggest meateater? Spinosaurus is the largest carnivore to have lived, weighing in at almost 10 tons and 60 feet in length. It lived about 100 to 93 million years ago in what is nowAfrica. Carrying an impressive sail, a mere arch of the back would raise the sail to almost seven feet. It is thought to have survived by eating fish, though judging by its size, Spinosaurus could have easily hunted smaller dinosaurs. It also has the longest-known head of any dinosaur, measuring 6 feet.

Reticulated python

The animals of prehistory were massive, but there are definitely some heavyweights that exist today. The longest snake is the reticulated python and it generally reaches lengths of up to 20 feet — though the record is 33 feet. They are usually tame but can be "a jumpy and unpredictable species." They are often kept as pets but can turn out to be too much for their owners (click here for a photo of nine men holding one). Python reticulatis is found in southeast Asia. It is non-venomous, but it could kill a grown man through strangulation.

The blue whale

There's one animal that exists today that measures up to the ancient behemoths. The blue whale can measure up to 100 feet in length and weigh as much as 150 tons. Today most blue whales only reach lengths of 75 to 80 feet because whale hunters tend to target the largest of the species, according to experts. About 50 people could stand on the tongue of an adult blue whale. Even a baby blue whale is gigantic — a newborn calf can be as long as 25 feet and drink as much as 100 gallons of its mother's milk a day. Endangered since the mid-1960s, only 10,000 blue whales are believed to still exist.

African elephant

While the blue whale is the largest animal in the ocean, the African elephant is the biggest land animal. The African elephant can live as long as 70 years, can stand as high as 13 feet in the shoulder and weigh as much as 14,000 pounds. They are perhaps among the cleanest animals on the planet, as National Geographic notes that the animal enjoys a good trunk shower, "often spray(ing) its skin with a protective coating of dust." Like the blue whale, its existence on Earth is threatened.

by