Fossil studies have shown that reptiles evolved from amphibian ancestors in the carboniferous period about 340 million years ago. Reptiles surpassed amphibians on land because they had survival advantages. These include they have a strong flexible skeleton, dry, scaly skin covering in moisture and eggs with protective shell so they won't dry out unlike amphibians who need water. By the late carboniferous period, which was 300 million years ago, reptiles split into more distinct groups according to their skull and skeletons. The Mesozoic Era is usually referred to the age of reptiles because this era witnessed dinosaurs on land, sea, and flying reptiles in the skies. However, some scientists say these dinosaurs were not reptiles they were birds ancestors. The earliest turtles, lizards, snakes, and their relatives evolved in the end of the Mesozoic Era. These animals survived the disasters that killed off the dinosaurs. The reasons for the mass extinctions are still being studied but some scientists say they have evidence that a giant asteroid or comet hit the earth causing climate change that dinosaurs could not survive. .
The evolution of reptiles to mammals varies slightly. For one, reptiles do not have hair or fur and the mammary glands to nourish their young. In addition, reptiles have a mouth filled with teeth that are not uniform in size and shape but they all have the same cone-shaped form. In reptiles, the lower jaw has several bones, which connect to the quadrate bone in the skull and the angular bone in the jaw. Mammals have one bone in the jaw to connect to the skull. In mammals, there are three bones in the middle ear, but in reptiles there is one- the stapes. The reptilian skull is attached to the spine by a single contact where in mammals the contact is double faced. The classic reptile skull has a small hole, or third eye through which the pineal body, in mammals this is unknown.