Reptiles Alive LLC
Introduction to Reptiles and Amphibians

What is a Reptile?

Reptiles are animals from the class Reptilia.
There are 4 orders of the class Reptilia:

  1. Chelonia – Turtles and Tortoises
  2. Crocodilia – Alligators, caimans, crocodiles, gavials
  3. Rhynchocephalia – tuatara
  4. Squamata – amphisbaenians, lizards, snakes

General Characteristics of Reptiles:

  • Reptiles have a backbone. They are vertebrate animals just like mammals and birds.
  • Reptiles are covered in dry scales made of keratin, the same protein that makes up mammal hair and bird feathers.
  • Reptiles breathe air with lungs, the same as mammals and birds.
  • Most reptiles lay eggs on land. Some reptiles give birth to live young.
  • Most reptiles do not protect their eggs or young. Crocodilians, some snakes, and a few lizard species do protect their eggs and to some extent their young.
  • Most reptiles are cold-blooded or ectothermic meaning, “outside temperature.” This means the animal’s internal temperature changes with the temperature of the environment. Mammals and birds are endothermic meaning their temperature is regulated from within their own body.

Chelonians – Turtles

There are over 300 different kinds of turtles. Sea turtles swim through the warm oceans of the world with giant flippers, tortoises lumber across the land with strong elephant like legs, and terrapins paddle with webbed feet in freshwater habitats.

A turtle’s ribs and backbone form its hard shell. Covered in skin and scales, a turtle’s shell is considered and endoskeleton, just like a human’s skeleton.

Sea turtles can hold their breath for over an hour by using the powers of their amazing heart. The heart blocks off blood to the lungs and allows the blood to travel to only parts of the body needing oxygen while under water!

The giant galapagos tortoise, aldabra tortoise, and african spurred tortoise can live to be over 170 years old!


Crocodilia – Crocodiles and family

With toothy smiles and big strong tails, crocodilians number over 20 different species including crocodiles, alligators, caimans, and gharials. Gharials have very long, narrow snouts studded with sharp teeth.

Crocodiles and alligators are a bit more difficult to tell apart. Alligators typically have broader snouts and straight rows of ridges down their backs. Crocodiles have narrower snouts and irregular rows of ridges on their back. When a crocodile’s mouth is closed, its fourth tooth on the lower jaw fits into a notch on the outside of the upper jaw.

There are only two different kinds of alligators; the American alligator and the endangered Chinese alligator.

Crocodilians feed on insects, snails, shellfish, frogs, turtles, fish, mammals, and birds. Most crocodilian species are afraid of humans and will swim away when people are nearby. The large saltwater and Nile crocodiles are the exceptions – they have been known to attack humans.

Crocodilian eyes and nostrils are located on top of their head to allow them to see and breathe above the water’s surface. They are covered in bony armor to protect them from both their prey and predators. They are very well built to survive in their watery habitats.

We still have much to learn from crocodiles. We have found they are immune to some diseases, heal quickly, are intelligent, and are wonderful parents. Alligators even help other animals survive during droughts by digging water holes with their huge body. Sadly, many crocodilian species are endangered due to habitat loss and over-hunting for food and the skin trade.

It is interesting to note that crocodilians are more closely related to birds than lizards. The superficial resemblance of crocodilians to lizards is due to convergent evolution.

Sustained energy expenditure of a reptile and a mammal as a function of core body temperature. The mammal has a much higher output, but can only function over a very narrow range of body temperatures.

Rhynchocephalia – Tuatara

The tuatara is an unusual reptile unchanged since the days of the dinosaurs. Although they look much like lizards, tuataras have different skulls, teeth, and pelvic bones. Living only in New Zealand on a few protected islands, these reptiles prefer lower temperatures than other reptiles. Tuataras live for a long time, probably over 100 years!

Unfortunately, they are highly endangered due to habitat loss and introduced predators.


Squamates (Amphsbaenians, Lizards, & Snakes)

Scientists do not separate lizards and snakes or the strange amphisbaenians into groups, but classify them all in one order.


Amphisbaenians look a little like big worms, but like all reptiles, they have an internal skeleton made of bone and they are covered in dry scales. They are long and usually legless (although some have two front legs and no rear legs.) They are primarily fossorial, meaning they spend most of their lives underground.


Lizards are the most diverse group of reptiles. They come in a huge variety of colors, shapes, and sizes. Some lizards, such as the Komodo monitor (dragon), can grow over 10 feet long. Others, like the Jaragua lizard, are able to curl up on a dime.

A typical lizard has external ears, four legs, claws, eyes with eyelids, and tails. Scientists have found that lizards can see color, and some can even see in the ultraviolet wavelengths. Excellent eyesight allows the creatures to snatch bugs out of the air and to see spectacular mating displays.

A lizard’s sense of smell and taste is very acute. Monitor lizards even have a forked tongue like a snake to enhance their ability to smell.

Lizards have found remarkable ways to survive. Many are covered in spines, some can stick to trees, most are able to lose their tails and grow them back, others change colors, a few glide out of trees, and one species can even run across water!

Compare and Contrast: Snakes vs. Lizards

  • All snakes are legless, but some lizards are legless too!
  • All snakes have no ears, but some lizards lack ears as well.
  • All snakes lack eyelids, but some lizards also lack eyelids.
  • Snakes have forked tongues, but so do many lizards.

Confused yet? Don’t worry, from now on we will discuss snakes and lizards as separate groups. Whew! (and you were worried)



Snakes are one of the most misunderstood group of animals on our planet. Many people fear snakes because of the myths and falsehoods perpetuated by the media and our society. Learning about snakes is a great way to overcome fears about snakes.

Snakes are reptiles that have no legs, ears, or eyelids. Snakes are dry, not slimy, as their scales are made of keratin, the same protein human hair and fingernails are made of.

A snake’s forked tongue cannot sting or hurt you. A snake that is constantly flicking out it’s tongue is simply interested in its surroundings, kind of like the “sniffing’ of a dog. Chemicals in the snakes surroundings, or “scents patricles,” stick to the tongue as it waves it around. Then the scent laden tongue deposites these particles onto a tissue pad on the floor of the mouth and that tissue pad is then pressed to the roof of the mouth transferring particles to the vomeronasal organ (a small hole in the roof of the mouth) sending instant messages about what it detects to the brain.)

Remarkable heat sensing pits light up the night for some lucky snakes. Rattlesnakes, pit-vipers, copperheads, boas, and pythons are able to distinguish in vivid detail differences in temperature allowing them to navigate and catch prey in complete darkness.

All snakes are carnivores. To catch prey, a snake must either bite it with fangs and inject venom, or use its body to subdue the animal using strong muscles. Swallowing the food is a challenge for an animal with no arms or legs! Their jaws are not strong enough to chew their food. Tiny curved teeth hook on to the food item, and allow it to only go in one direction, down the throat!

A snake’s head may appear too small to swallow many food items. Snakes can open both their upper and lower jaws exceptionally wide. The lower jaw includes two jaw bones connected in the middle with a stretchy ligament, so the mouth can open wide sideways as well. One side of the jaw holds the prey while the other side of the jaw slides forward, walking the food further into their mouth.

The largest snakes in the world are the anaconda and reticulated python, both able to grow up to 30 feet long and weigh several hundred pounds.

Snakes benefit our us and our planet in many ways. Snake venoms are used to make medicine to treat cancer, heart disease and other illnesses. Snakes prey on rodents, insects and other agricultural pest species. Other species of animals, including eagles, rely on snakes as food sources. Snakes are natural and integral part of our world’s ecosystems. If you see a snake, just leave it alone.


What is an Amphibian?

Amphibians are animals from the class Amphibia.

There are 3 orders of the class Amphibia:

  1. Anura – frogs and toads
  2. Caudata – newts and salamanders
  3. Gymnophiona – caecilians


  • Amphibians have a backbone and an internal skeleton made of bone. They are vertebrate animals like birds, mammals, and reptiles.
  • Amphibians are cold-blooded or ectothermic. They cannot internally regulate their own body temperature.
  • Most amphibians start life as an aquatic larvae (tadpole) breathing the water with gills and then go through metamorphosis to become adults with lungs which breathe air. Exceptions include the lungless salamanders, such as red-backed salamanders (Plethodon), that lay their eggs on land and even guard them!
  • Most amphibians do not have scales (the exceptions are some of the caecelians) and their skin is permeable (that means molecules and gases can pass through their skin).

Anura – Frogs & Toads

Frogs and toads have a similar body shape – squat with longer back legs and shorter front legs and, as adults, most species have no tail. Some frogs have moist, slimy skin, whereas other frogs (toads) have dry skin covered in warts. All frogs have skin that is poisonous to some degree, the dart frogs of South America being the most famous for this trait.
All frogs are carnivores and depending on their size, will eat nearly anything they can swallow. Prey items include: insects; fish; smaller frogs; small snakes, lizards, turtles, and baby alligators, small birds, and small mammals.
Frogs are found in a variety of habitats in freshwater, on land, and in treetops too. Scientists studying ecosystems use the presence or absence of frogs to determine the health of the area being studied. As Kermit the Frog once said, “Shopping centers are nice and all, but a good swamp is hard to find.”

Caudata – Newts & Salamanders

The definition of the word caudate is “having a tail.” Salamanders are a group of amphibians that have long tails, long bodies, and distinct heads. Most salamanders are very small, less than 5 inches when fully grown. A few salamanders can get big, including the American hellbender and the Asian giant salamanders which can grow to over 2 feet long.
Salamanders are generally found in the temperate zones in cool forests. Most salamanders are either aquatic or terrestrial, but a few are arboreal.
The Appalachian mountains in the eastern United States are home to more species of salamanders than any other region of the world. One species, the red-backed salamander, has such large population densities that in some areas, it is considered the most abundant vertebrate animal.

Gymnophiona – Caecilians

Caecilians have an appearance very similar to earthworms. They are legless and have rounded, blunt heads and tails. Their bodies even have a grooved, segmented appearance. Also like earthworms, caecilians are burrowers and use their tough, compact skull to tunnel through the earth.

Caecilians are carnivores and feed on worms, insects and other creatures smaller than themselves.

Caecilians are found in the tropics in South America, Africa, and Asia.



  1. Both classes are vertebrate animals that have internal skeletons made of bone.
  2. Both are ectothermic.
  3. Most species of both amphibians and reptiles do not protect their eggs or young.


  1. The skin of amphibians is glandular, highly permeable to air and water, and is usually covered in slimy mucus. The skin of reptiles is covered in dry keratin scales and is not very permeable to air or water.
  2. Amphibian eggs do not have a shell and are usually laid in water. Reptiles either lay shelled-eggs on land or give birth to live young.
  3. Most amphibian young are born physiologically different from their adult form and must go through metamorphosis to develop into adults. Reptiles do not go through metamorphosis.


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