Home >> Science & Nature >> Animals & Science

Types of Lizards, Reptiles & Snakes

Reptiles have been around for over 300 million years. They are cold-blooded animals, meaning that except for insulation or evaporation, their body temperature is the same as their environment. They have lungs and breathe air, and their skin is usually covered with scales or plates. Their teeth are the same size and lack the specialization seen in mammals. Most reptiles lay eggs, but a few give birth. Most reptiles are harmless and are beneficial to humans because they eat rodents and insects.

Lizards
- Lizards range in size from 10-foot-long komodo dragons to 4-inch-long geckos.
  
  Lizards are found mostly in the warmer parts of the world, although a few species live as far north as Canada. Most have four legs with five toes on each foot as well as eyelids and ear openings on the sides of the head. The glass snake, one of the few limbless species, grows to three feet and eats insects. The horned lizard, which lives only in the Western United States, has a toad-like body and spines around its head, which give it its name. When agitated, it can squirt blood from the corner of its eye. The Komodo dragon is a 10-foot-long lizard native to a few islands in Indonesia. Their saliva contains so much bacteria that a bite can result in death from blood poisoning. In addition, the Komodo dragon is now thought to be venomous.
Turtles and Tortoises
- A box tortoise can pull its head and legs all the way into its shell.
  
  Other reptiles include the mostly aquatic turtles and the land based tortoises. They are very old and unusual reptiles that appeared about 200 million years ago and have remained basically unchanged for 150 million years. The top shell, or carapace, is formed from overgrown and widened ribs. All turtles lay eggs and bury them in the ground, even the aquatic sea turtles. Other turtles are the alligator snapper, which reaches 30 inches long and may weigh 150 lbs. Its jaws can maim a hand or foot. Meolania, an 8-foot-long tortoise who lived less than 2 million years ago, had spikes on its head. Its tail was ringed with bony armor and ended in a spiked club.
Alligators and Crocodiles
- The sex of a crocodilian is determined by the heat of egg incubation.
  
  Alligators and crocodiles form their own group of reptiles. Alligators have blunter, broader snouts than crocodiles. Both will eat fish, turtles, birds, and other aquatic life. Both reptiles lay eggs that are hatched by the heat of the decaying vegetation the mother heaps over them. Crocodiles prefer saltwater and will even swim into the ocean, while alligators like fresh water. A number of crocodile species exist but only two alligator species: the American alligator and the somewhat docile Chinese alligator.
Snakes
- Most snakes are harmless.
  
  Snakes lack limbs eyelids or ear openings. Each side of the snake's lower jaw can move separately, which allows it to swallow prey larger than its head. The teeth of snakes are small and hooked and the fangs of venomous snakes are grooved or hollow to allow the passage of venom. Interesting snakes are the coach whip, a log slender snake that lives in the warmer parts of the United States and grows to about 5 feet long. It's nonvenomous but irritable and will strike and lash if handled. Rattlesnakes are the largest venomous snakes in the United States; the Eastern diamondback can grow to about 5 feet long. The rattle is a horny structure at the end of the tail that grows another segment whenever the snake molts.

Animals & Science