Zoology

Understanding the four Groups of Reptiles



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There are four main groups of reptiles and they are turtles and tortoises, lizards and snakes, crocodiles and alligators, and the tuatara. Let's take a closer look at each group.

Group 1: Tuatara

Tuatara are classified as an endangered species. They are the only lizard looking reptiles that resemble their extinct dinosaur relative and that is why they are sometimes referred as the "living fossil". Tuataras are nocturnal, they enjoy cool weather, they have spikes that run down their spine, and they have a third eye on the top of their head that is visible when the are young but as they get older it is covered up with scales making it hard to see. The third eye is not functional but the tuatara may use it to tell the difference between night and day.



Tuataras do not stop growing until they are 30 years old, and the do not reach full maturity until they are between 13 and so years old. They grow to be 20 to 31 inches long, they weigh about 1 to 3 pounds, the female lays 1 to 19 eggs at a time which take 11 to 16 months to hatch. They live in burrows often belonging to birds and the hunt for food at night which consist of insects, birds, bird eggs, and earthworms.



Group 2: Alligators and Crocodiles

What is the difference? Alligators have "U" shaped noses, when their mouth is closed, you cannot see their teeth, and they prefer to live in fresh water. Crocodiles have "V" shaped noses, when their mouth is closed you can see their teeth, and they tend to live in saltwater. Even though alligators and crocodiles may look different, they along with caimans and gharial are grouped together and are known as "crocodilians" also known as "crocs".



Crocodilians have perfect hearing. They have slits on the side of their head that closes up when they dive under water to keep the water out. They are carnivores meaning they eat meat. They do not chew their food, so they tear and swallow. Female crocs are called cows and the dig holes in the ground and lay eggs. Large crocs lay 20 to 60 eggs and smaller ones lay10 to 20. Incubation is 55 to 110 days, the baby croc will weigh 2 to 2 ounces at birth, they can grow over 2,000 pounds, and they can live at least 50 to 75 years.



Group 3: Turtles and Tortoises

What is the difference? Turtles tend to have webbed feet and spend most of their lives in the water. Tortoises do not have webbed feet and they spend their time on the land. Terrapin lives near water and spends its time equally on the land and in the water.



Turtle and tortoises have hard shells on their back. Their shells are made up of 59 to 61 bones covered by plates which are called scutes and is part of their skeleton. They do not have ears and they depend on vibrations, and changes in the water pressure to find their food. Turtles and tortoises lay eggs which they bury in the vegetation, sand, or soil. They do not take care of the eggs they lay. The eggs and hatchlings are on their own. Turtles and tortoises do not have teeth. Some are herbivores ( they only eat vegetation) and some are omnivores (they eat plants, and meat such as worms, fish, and insects).



There is about 250 species. The largest leather back turtle shell length can get up to 8 feet. The smallest bog turtle shell length is between 3 and 4 inches. The heaviest leather back turtle weighs up to 1800 pounds. The lightest Speckled Cape Tortoise weights up to 5 ounces. The land tortoise can live up to 150 years and turtles that live in the water can live up to 70 years. Some lay a few eggs and some lay 100 or more. Incubation takes 2 months to 1 year depending on the species.



Group 4: Lizards and Snakes

Lizards are closely related to snakes and some look like snakes because they do not have legs. There are over 4,675 different species. Most lizards have moveable eyelids and snakes do not. Some lizards live in trees, or in the water, but most of them live on the ground. They smell with their tongues, they blink their eyes like humans, and some eat vegetation and meat, and others just eat vegetation. Lizards lay eggs and the mother does not stick around to protect her young. They are on their own.



Snakes are covered with scales, they have no ears, no eyelids, no legs, no arms, just a long slender body. They can live anywhere except in the cold. There are more than 3,000 species. They are carnivores which mean that they will eat any type of meat, big or small. Some snakes lay eggs (oviparous), and some are live bears (ovoviviparous). The largest Python is 33 feet, and the heaviest Anaconda is about 500 pounds.

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