A reptilian heritage is evident in all amniotes The class Reptilia is a diverse group with about 7,000 extant species and a wide array of extinct forms. Reptiles possess several adaptations to live on land not found in amphibians. Gas exchange via lungs although many turtles also use moist cloacal surfaces. Dioecious with sexual reproduction and internal fertilization. Most are oviparous and produce an amniotic egg .
Reptiles are ectotherms and use behavioral adaptations to regulate their body temperature.
An animal that uses behavioral adaptations to absorb solar energy and regulate its body temperature. Due to ectothermy, reptiles can survive on a much lower caloric intake than mammals of comparable size. Reptiles were abundant and diverse in the Mesozoic era. Ancestors were probably Devonian amphibians. Two waves of adaptive radiation resulted in reptiles being the dominant terrestrial vertebrates for 200 million years.