It’s World Lizard Day! Today is the day to celebrate all things lizardy. Come take a journey with us as we discuss these scaly scamps!
What is a lizard, exactly? Lizards are reptiles belonging to the order Squamata, which also includes snakes. Like most reptiles, they are covered in scales, and like snakes they periodically shed their skins. They typically have four legs, although some lizards are legless. The first lizards likely appeared in the late Triassic period, over 200 million years ago, and have evolved to become an extremely diverse group that contains over 6,000 present day species.
Lizards come in many different shapes and sizes, from the tiny chameleon known as Brookesia micra that grows barely longer than an inch, to the Komodo dragon which can grow as long as ten feet. Many lizards have unique features that can make them quite strange-looking. Iguanas, for example, have large spines along their backs, as well as prominent dewlaps, which are large flaps of skin that hang from the throat. Others, like the bearded dragon, are covered in pointed, spiny scales that give them a fearsome look, despite their docile temperament that makes them popular as pets. But perhaps the oddest physical trait is found in the frilled lizard, so named because of the large umbrella-like frill around its neck that it uses to intimidate and scare off would-be predators.
One of the most well-known and iconic lizard adaptations is found in the chameleon. These lizards are loaded with interesting and distinguishing characteristics, including large head shields, curly prehensile tails, independently moving eyes, and unique arrangement of toes that helps them climb trees. But by far their most notable features are their long sticky tongues, which they use to catch insects and other prey, and their ability to change color. This ability is used to help the chameleon blend into its environment, but also as a way for chameleons to communicate with one another. For example, chameleons display bright colors to one another to signal aggression. Tiny structures under their skin called guanine crystals are used in the process: The lizards move them around to alter the wavelengths of light reflected off the crystals, which produces a different color.
Another ability which is equally as strange, though less well-known, is found in the horned lizards of western North America. These lizards are covered in spines to help protect them, but that’s not the only defense they have. They are also capable of squirting blood from their eyes when confronted by a predator, confusing the attacker so the lizard can make an escape. As if that weren’t enough, the blood contains chemicals that make it taste bad to mammals.
Though the horned lizard’s defense tactic is gross, it’s not dangerous. That’s not always the case with lizards, though. Some lizards, like some snakes, are venomous. The Gila monster produces a potently toxic venom, but as it only makes small amounts and is quite slow and sluggish, bites are not common and usually do not cause much lasting harm to humans. It was once believed that Komodo dragons and other monitor lizards had bacteria living in their saliva that caused their bites to swell painfully, but it is now believed that they may actually produce their own venom. Unlike the Gila monster, Komodo dragons are known to be quite dangerous to humans. Though rare, attacks occasionally occur, since their large size means they might see humans as prey.
Most lizards, though, are completely harmless. In fact, even venomous lizards can be beneficial to humanity. The Gila monster’s toxin helps lower certain sugar levels in blood, which can help people with diabetes. So the next time you see a lizard, remember how lucky we are to have them!
Bernie’s Bonus Fun Fact: The largest land lizard ever discovered is the Megalania, a relative of the Komodo dragon that lived up until around 50,000 years ago. These Australian lizards may have grown up to 20 feet long. However, the largest lizards that ever lived were the sea-dwelling mosasaurs, including Mosasaurus and Tylosaurus, which lived in the late Cretaceous Period and could grow up to 50 feet long.