Reptilia

Reptilia is a tetrapod clade comprising turtles, lepidosaurs, crocodilians, birds, and their ancestors. Its members are amniotes, and modern classification includes birds within the clade.

Amniota: A tetrapod clade whose embryos develop within protective extraembryonic membranes. Reptilia is nested within this broader group of land-adapted vertebrates.
Amniotic egg: An egg whose membranes support embryo development on land without direct dependence on open water. The amniotic reproductive system is a defining inheritance of reptile ancestry.
Linnaean taxonomy: A hierarchical system for naming and classifying organisms, established by Carl Linnaeus. Traditional classifications grouped reptiles apart from birds, unlike clade-based usage.
Hylonomus: An extinct Carboniferous amniote known from fossils in Nova Scotia, about 315 million years old. It is among the oldest known animals often identified as a reptile.
Sauropsida: The amniote lineage that includes reptiles and their extinct relatives. This lineage provides a widely used framework for reptile relationships.
Ectothermy: A condition in which body temperature depends largely on heat from the environment. Most living reptiles regulate activity by behavior and environmental heat.
Cladistics: A method of classifying organisms by shared derived traits and common ancestry. Cladistics places birds within Reptilia because they descend from reptilian ancestors.
Captorhinidae: An extinct group of early reptiles that lived mainly during the Permian Period. Captorhinids document early reptile diversification before the rise of modern groups.
Diapsid: A reptile traditionally characterized by two temporal openings on each side of the skull. Most living reptiles, including birds, belong to this major reptile lineage.
Keratin: A structural protein that forms durable tissues such as scales, claws, feathers, and hair. Keratinized coverings help limit water loss and protect reptile bodies.

Linked from 9 pages