REPTILIA - the Reptile Family

Reptiles are recognized as the first fully land vertebrates, evolving 250 million years ago and in the Mesozoic era (195 to 65 millions BC ) or Age of Reptiles, they flourished and were the dominant animals on the planet. For still unknown reasons, this class of animals started then to decline and presently only 4 orders of the original 23 orders have existing species. Members of the other 19 major orders, including the mighty dinosaurs, became extinct over million of years and only fossils remain of them.

Only the Rhynchocephalia order with only two species of tuataras or beakheads still alive, are present only on a few islands off the coast of New Zealand.

Squamata is the largest order with 2500 snakes and 2500 lizards worldwide.

Chelonia or Testudines, which comprise 250 turtles and tortoises have some important species present on Galapagos and the mainland.

Crocodilia, where 22 species of alligators, caimans, gavials and the proper crocodiles are grouped together, are considered the true remnants of the golden Age of Reptiles. The State of Florida is the only place in the world where both alligators (American Alligator) and crocodiles (American Crocodile) exist in the same areas naturally.

Reptiles are a highly successful group of 6,547 different species. Class Reptilia is made up of the first animals to produce amniotic eggs. In this type of egg, the embryo develops in a fluid filled sac called an amnion. This prevents the egg from drying out, and allowed the reptiles to live only on land. Reptiles have tough skin made of the protein keratin. Since reptiles do not need to breathe through the skin, it is much thicker than the skin of amphibians. Reptiles can be distinguished from amphibians by their scaly skin. In addition, reptiles either lay eggs or give birth to live babies. They do not have the larval stage like amphibians (the frog has the tadpole stage). Reptiles periodically shed their skin in a process called molting. Another adaptation allowing reptiles to live on land is a well-developed respiratory system with branched bronchial tubes in their lungs. Reptiles have teeth adapted for holding prey rather than chewing it because most species in this class swallow their prey whole. Reptiles have good hearing and vision and a tongue is used for smell as well as taste. The only disadvantage to reptiles is that they are ectothermic, meaning they warm up by absorbing heat rather than generating their own heat, like birds and mammals. Since reptiles are cold blooded, they do not need to consume as much food to maintain a body temperature. This gives them a great advantage over warm-blooded mammals, especially in desert areas where vegetation can be sparse. Most reptiles are found in the temperate and tropical regions of the world but some of them can survive in colder regions, going into hibernation when winter hits them.