Reptiles have been around some 300 million years, and our planet has seen its fair share of gigantic scaled beasts during its history. That said, only a few behemoths from the golden age of reptiles still exist today.
Here we present the five largest reptiles on Earth; the biggest in the four commonly recognized reptilian orders.
1. Saltwater Crocodile (Order: Crocodilians)
The saltwater crocodile is the largest living reptile in the world, growing to a length of over 6 meters (20 ft). These mean-toothed giants are able to crush the skulls of cows between their jaws and, should the mood take them, can easily eat a human. The areas of largest croc populations in Australia are clearly marked, so people know where not to stray and so avoid ending up as a croc's lunch.
Saltwater crocodiles range from the tip of Southeast Asia to Australia. As their name implies, they are even known to take to the sea, and have reached locations as remote as the Sea of Japan. Crocodilians belong to an order even more ancient than dinosaurs, so the saltwater crocodile gives us a glimpse into the halcyon days of its gigantic prehistoric ancestors.
2. Leatherback Sea Turtle (Order: Testudines)
Leatherback sea turtles can measure over 2 meters (7 ft) in length, with a flipper span of almost 3 meters (8 ft), and are unique among turtles thanks to their lack of a hard, bony shell. Instead, their ridged, leathery carapace is built for speed, making them the fastest reptiles on Earth — as well as among the most humungous. Speed capacity and lots of fatty tissue keeps them warm for long sea voyages and deep dives of up to 1,200 meters (4,000 ft).
A leatherback's diet consists mostly of jellyfish — so much so that their populations keep jellyfish numbers in check. Sadly, they often mistake plastic bags for jellyfish, and many have died from ingesting plastic bags.
The eggs of leatherbacks are eaten in Malaysia, Thailand and parts of the Caribbean. This has also had a devastating effect on turtle populations. The Leatherback Trust is an organization dedicated to the preservation and survival of these giant yet vulnerable creatures.
3. Reticulated Python (Order: Squamata)
Did you know that pythons are expert swimmers, and that their sea voyages have distributed them among a variety of islands in the Indo-Australian Archipelago? Yet, as well as being at home in water, reticulated pythons are aggressive constrictors that suffocate their prey and ingest it whole. They have been reliably recorded at 6.95 meters (22.8 ft) — slightly longer than saltwater crocodiles, albeit nowhere near as heavy.
The world-beating length of the reticulated python has been disputed by claims of even larger green anacondas. Legends and movies about the snake certainly make it seem a fearsome predator. Anacondas have been found to reach 6.6 meters (22 ft), only slightly shorter than the reticulated python. Still, although anacondas chill and thrill us in stories, the reticulated python may be the more fearsome of these two serpentine heavyweights, being on record as having killed and eaten human beings.
4. Komodo Dragon (Order: Squamata)
Technically, lizards and snakes belong to the same order, but most lizards have legs, while snakes don’t, so we're representing the four-legged Squamata too! This king of lizards is a deadly hunter reaching lengths up to 3 meters (10 ft). Enter the komodo dragon. These bad boys hunt in the afternoon, ambushing their prey using their arsenal of powerful sharp claws, a strong tail, and a poisonous mouthful of deadly bacteria. The term ‘dragon’ certainly seems appropriate when sizing up these ferocious monsters.
While komodo dragons obviously can’t breathe fire, their saliva contains virulent strains of bacteria that grow with uncanny rapidity. These bacteria ensure that bites usually result in sepsis and fatal infection. And, like their mythological counterparts, which were immune to their own fire, komodo dragons are immune to their own poisonous secretions. Scientists have yet to discover how this is possible. We’ll leave the field research to them!
5. Tuatara (Order: Sphenodontia)
This guy may be a squirt in comparison to the other giants in the winners’ circle, but as the only surviving member of its order, the northern tuatara is the largest living, well… tuatara! While its closest living relatives are reptiles and snakes, the tuatara’s order can be traced back to the Mesozoic Era, from where it derives its distinctly unusual attributes.
While they may look like reptiles, tuataras actually have legs and brains that closely resemble those of amphibians. They possess three eyelids on each eye and a third ‘parietal’ eye on the top of their heads, possibly used to detect day and night cycles. Their backbone vertebrae resemble fish, and their rib features are more typical of birds. Meanwhile, their spiny tails and back plates are more crocodilian than lizard-like. The creature is an anomaly in the modern world of reptiles, and lives exclusively on the offshore islands of New Zealand.
While saltwater crocodile populations are currently well represented in Australia, many other reptiles are in need of protection from habitat loss or hunting. For information about the conservation and populations of reptiles big and small, search the International Union for Conservation of Nature (IUCN).