What makes crocodiles different from other reptiles

This mode of locomotion takes a lot of energy, and seems to be used primarily to clear ground obstacles. Amazingly, some crocodiles can also gallop, pushing off with their hind legs and moving their hind and forelegs alternately in pairs. Galloping crocodiles have been clocked at speeds over 17 kph and, over short distances, in an ambush situation, they can easily chase down most humans if they are taken by surprise.

However, they are short distance runners, not interested in a long chase, and most fit humans can probably outrun them in a sprint assuming they respond quickly to the ambush! Tuataras have a primitive diapsid skull with biconcave vertebrae.

They measure up to 80 centimeters and weigh about 1 kilogram. Although superficially similar to an iguanid lizard, several unique features of the skull and jaws clearly define them and distinguish this group from the Squamata. They have no external ears. Tuataras briefly have a third parietal eye—with a lens, retina, and cornea—in the middle of the forehead. The eye is visible only in very young animals; it is soon covered with skin.

Parietal eyes can sense light, but have limited color discrimination. Similar light-sensing structures are also seen in some other lizards. In their jaws, tuataras have two rows of teeth in the upper jaw that bracket a single row of teeth in the lower jaw. These teeth are actually projections from the jawbones, and are not replaced as they wear down. Figure 2. This tuatara from New Zealand may resemble a lizard but belongs to a distinct lineage, the Sphenodontidae family.

Figure 3. Both are found on all continents except Antarctica. Lizards and snakes are most closely related to tuataras, both groups having evolved from a lepidosaurian ancestor. Squamata is the largest extant clade of reptiles.

Most lizards differ from snakes by having four limbs, although these have often been lost or significantly reduced in at least 60 lineages. Snakes lack eyelids and external ears, which are both present in lizards. There are about 6, species of lizards, ranging in size from tiny chameleons and geckos, some of which are only a few centimeters in length, to the Komodo dragon, which is about 3 meters in length.

Some lizards are extravagantly decorated with spines, crests, and frills, and many are brightly colored. Some lizards, like chameleons Figure 3 , can change their skin color by redistributing pigment within chromatophores in their skins.

Chameleons change color both for camouflage and for social signaling. Lizards have multiple-colored oil droplets in their retinal cells that give them a good range of color vision. Lizards, unlike snakes, can focus their eyes by changing the shape of the lens. The eyes of chameleons can move independently. Most lizards are carnivorous, but some large species, such as iguanas, are herbivores.

Some predatory lizards are ambush predators, waiting quietly until their prey is close enough for a quick grab. Others are patient foragers, moving slowly through their environment to detect possible prey. Lizard tongues are long and sticky and can be extended at high speed for capturing insects or other small prey. Traditionally, the only venomous lizards are the Gila monster and the beaded lizard. However, venom glands have also been identified in several species of monitors and iguanids, but the venom is not injected directly and should probably be regarded as a toxin delivered with the bite.

Figure 4. A nonvenomous snake. The garter snake belongs to the genus Thamnophis, the most widely distributed reptile genus in North America. Specialized features of the jaw are related to adaptations for feeding that have evolved to feed on relatively large prey even though some current species have reversed this trend.

Snakes are thought to have descended from either burrowing or aquatic lizards over million years ago Figure 4. They include about 3, species, ranging in size from 10 centimeter-long thread snakes to 10 meter-long pythons and anacondas. All snakes are legless, except for boids e. Like caecilian amphibians, the narrow bodies of most snakes have only a single functional lung. All snakes are carnivorous and eat small animals, birds, eggs, fish, and insects.

They also eat live locusts. In the wild, crocodiles will clamp down on their prey with their massive jaws, crush it, and then they will swallow the prey whole. They do not have the capability to chew or break off small pieces of food like other animals. To help with digestion, crocodiles swallow small stones that grind up the food in their stomachs.

Thanks to their slow metabolisms, crocodiles can survive for months without food. During the Mesozoic Era , about million years ago, the Crocodilia order was one of the top animals on the food chain.

Today, crocodiles are found in the tropical habitats of Africa, Asia, Australia and the Americas. They normally live near lakes, rivers, wetlands and even some saltwater regions. One of the largest known populations of American crocodiles is found in the Dominican Republic's at a large saltwater lake called Lago Enriquillo, according to National Geographic.

Crocodiles live in tropical climates for a reason. They are cold-blooded and cannot generate their own heat. During colder months, they hibernate or go dormant. Crocodiles will also go dormant during long periods of drought. To create a place to hibernate, they dig out a burrow in the side of river bank or lake and settle in for a long sleep. Crocodiles lay 10 to 60 eggs at a time.

The hatchlings stay in their eggs for 55 to days. They are 7 to 10 inches How long a crocodile lives depends on its species. Some only live to around 30 years, while others live up to 75 years. It is considered critically endangered and has a population of only about 4, Poaching is a constant threat to the crocodile species. The American crocodile is also considered vulnerable by the International Union for Conservation of Nature and Natural Resources , but their populations are increasing.

Crocodiles are often confused with alligators, but there are some easy-to-spot differences. An alligator's jaw is U-shaped, while a crocodile has a V-shaped jaw, according to the San Diego Zoo. Crocodiles also have teeth that stick up over their upper lip when their mouths are closed.

Another difference between alligators and crocodiles is that crocs have salt glands on their tongues. These modified salivary glands help crocs tolerate living in salt water. Alligators and caimans have lost the ability to secrete excess salt through the tongue glands and therefore, they prefer to live in freshwater areas.

When a crocodile loses a tooth, it is quickly replaced. These reptiles can go through 8, teeth over a lifetime. Crocodiles don't sweat.