Crocodiles are not lizards, and it is wrong to say that they are the biggest lizards on earth. Crocodiles and lizards are both reptiles, but lizards belong to a separate group of animals than crocodiles.
Crocodiles are part of the Crocodilian order—an order of semi-aquatic reptiles that first appeared 95 million years ago. They are the closest relatives of birds, as they both came from the same ancestor, the archosaur.
What is a Reptile?
Reptiles are animals that belong to the class Reptilia. They are tetrapod vertebrates, which means they have four legs.
One should take note that reptiles are not amphibians. Reptiles, unlike amphibians, do not have an aquatic larval stage.
An example of the aquatic larval stage is the egg of a frog—it gets fertilized in the water, and the offspring hatches there. They will live in the water for a time and then move on land.
Here are some of the most common examples of reptiles:
In traditional classification systems, birds are a separate class from reptiles. However, since crocodilians are closer relatives of birds, the modern classification system now includes birds within the Reptilian class.
The study of reptiles, including modern amphibians, is herpetology. Therefore, experts in snakes and crocodiles are called herpetologists.
Related Article: What Animal Eats Crocodiles?
What is a Lizard?
A lizard is a reptile that belongs to the sub-order Sauria. There are more than 4,000 species of lizards, all of which are scaled animals. Although lizards look like snakes, lizards have eyelids while snakes don’t.
Lizards live in many types of habitats, except in extremely cold environments like Antarctica. Most lizards live in warm regions, but some are present near the Arctic Circle in Europe and Asia.
Lizards are the most diverse of all reptiles. They vary in shapes and sizes, some of which are as small as two centimetres. The biggest lizards are the monitors, and the Komodo Dragon is the most dangerous lizard, whereas the Crocodile is the most dangerous of all reptiles.
Lizards also have varying diets. While some say they are carnivores, there are plant-eating lizards too.
Not all lizards have legs. Some are limbless and closely resemble snakes. Others have long hind legs, and some are even capable of bipedal locomotion.
Some lizards have wings—it does not make them fly, but rather helps them glide as they jump from one tree branch to another. Some lizards have colorful ornaments, called frills. Frills can either be used to attract a mate or scare a predator.
Read Also: 30 Animals Like Lizards
What is a Crocodile?
A crocodile is a reptile that belongs to the order Crocodilia. This order has three main branches called Crocodylidae, Alligatoridae, and Gavialidae.
The true crocodile, like the saltwater and Nile crocodile, belongs to the family Crocodylidae. Although they look similar to gharials and alligators, they are of different biological families.
Crocodiles are huge predators, and they are semi-aquatic. They live in various habitats in the world, and there are species that thrive in saline and freshwater environments.
Although lizards are also predators, crocodiles are much more aggressive and active hunters. Both, however, use the lie-and-wait predatory strategy.
Read More: Can a Human Outrun a Crocodile?
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Why are Crocodiles Not Lizards?
There are many physical differences between lizards and crocodiles, but the main definitive difference is their ancestry/biological taxonomy. Lizards evolved down a completely separate evolutionary branch than crocodiles.
Crocodiles, being part of the crocodilian family, have big heads. These heads are important because their size gives them the power to bite big prey. Lizards, on the other hand, have small heads.
Crocodiles do not have venom, while some lizards do. For example, the Komodo Dragon has venom that kills its prey.
Contrary to popular belief, Komodo Dragons do not have toxic bacteria in their saliva. Study shows that they have venom in their bites.
A vast majority of lizards live on land, not water. On the other hand, crocodiles live in bodies of water. Crocs are also flexible—there are species that thrive in saline water, and there are those that live in freshwater. Most lizards live on the ground. There are other species that live in trees or under rocks.
Another difference is the way they lay eggs. Crocodiles build nests and care for their young after hatching. This is not to say that lizards do not care for their young. Some of them do, but most of them do not.
One interesting fact about lizards is that they have no gizzards. Crocodiles, on the other hand, are the only reptiles that have a gizzard since they evolved from a common ancestor with birds.
Related Article: Can Crocodiles and Alligators Live Together?
Are Lizards More Dangerous Than Crocodiles?
Most lizards are not as dangerous as crocodiles, however there are some dangerous lizards like the Komodo Dragon that can be fatal to humans. Komodos arethe most dangerous, and also the largest extant living lizard species alive today, while Crocodiles are the largest reptile overall.
A monitor lizard, the Komodo lives on the Komodo Island in Indonesia. Like a crocodile, it is predatory, and it is huge. However, it can only grow up to 10 feet in length, while crocodiles can reach sizes of up to 20 feet.
Adult Komodo Dragons are cannibals. They eat juveniles, and they even sometimes eat fellow adult Komodo Dragons.
What makes a Komodo Dragon dangerous is its speed. It can run and attack a human being. There have been a number of attacks reported from 2000 to 2014. It was in 2007 when a fatal attack occurred—33 years after the first reported one.
Although this lizard is a predator, its main diet is carrion—rotting flesh. In the wild, it will also ambush pigs and cattle. They have venomous bites that inhibit blood clotting, killing the prey from rapid blood loss. It also has bacteria in its mouth that can cause infection to its prey.
Crocodiles are not lizards. Lizards are also reptiles, but they are squamates. While both crocodiles and lizards are reptiles and predators, crocodiles are much more fearsome. They are also bigger.
There are many living species of lizards today, but only about 27 for the crocodylian family. This includes the alligators, caimans, and gharials. Lizards live mostly on land and trees, but crocodiles need water to survive.
Stuart is the editor of Fauna Facts. He edits our writers’ work as well as contributing his own content. Stuart is passionate about sustainable farming and animal welfare and has written extensively on cows and geese for the site.