AN INTRODUCTION TO REPTILES
In the carboniferous period of palaeozoic era “Reptiles” arose from Labyrinthodont Amphibians. In the Mesozoic era “Reptiles” dominated the entire world and that era is called "GOLDEN AGE OF REPTILES".
Cotylosauria’ is considered as “stem - reptiles”. They closely resemble the Labyrinthodont amphibians. It is not easy to distinguish these two groups separately.
In the Mesozoic era giant dinosaurs dominated the earth. In the late cretaceous period of Mesozoic era they became extinct.
In the present day world nearly 5,000 known species of reptiles are living. Reptiles are poikiothennic vertebrates. They are first true land vertebrate’s. They are the first amniotic group of vertebrate animals.
The Present day reptiles are sphenodon, lizards, snakes, turtles and crocodiles.
The Reptiles origin from labyrinthodont Amphibians in the carboniferous period of Paleozoic era. Present day living Reptiles are 5,000 species. They have an endoskeleton of dry epidermal scales and in some, bony dermal plates are present.
The Reptiles flourished in the Mesozoic era. Gant Dinosaurs dominated the earth and seas. Mesozoic era is the “Golden age of Reptiies”. Most of the giant Reptiles became extinct in late cretaceous period of Mesozoic era era.
GENERAL CHARACTERS OF REPTILES
- Reptiles are cold blooded Vertebrates.
- Reptiles are terrestrial (or) aquatic animals.
- The body of Reptiles is covered with horny scales (or) bonyscutes.
- In Reptiles Skin is dry.
- Glands are absent in the skin of Reptiles.
- Four limbs are present. They are pentadactyl (having 5 fingers).
- Skull occipital incompletely.
- In Reptiles Vertebrae are gastrocentrous.
- In Reptiles Ribs from a true sternum.
- Respiration is carried on by the lungs.
- In Reptiles Heart is divided into two auricles and ventricle is divided into2 chambers incompletely.
- Right & left aortic arches are completely formed.
- Red blood corpuscles are nucleated in Reptiles.
- In Reptiles Kidneys are meta nephric. Each kidney is provided with separate ureter.
- In Reptiles Twelve pairs of cranial nerves are seen.
- Cloaca is present.
- Fertilization is internal. Eggs are laid on land.
- In Reptiles Extra embryonic membranes are present during the development of the embryo.