Cladogram showing relationships of extant members of the Sauria. Numbered items are:
1. Tuatara
2. Lizards
3. Snakes
4. Crocodiles
5. Birds
"Lizards" are paraphyletic. Branch lengths do not indicate divergence times.
The first turtles are believed to have existed in the Mesozoic, around 200 million years ago. Their exact ancestry is disputed. It was believed that they are the only surviving branch of the ancient clade Anapsida, which includes groups such as procolophonoids, millerettids, protorothyrids and pareiasaurs. All anapsid skulls lack a temporal opening, while all other extant amniotes have temporal openings (although in mammals the hole has become the zygomatic arch). Most anapsids became extinct in the late Permian period, except procolophonoids and possibly the precursors of the testudines (turtles).
Feathers are one of the epidermal growths that form the distinctive outer covering, or plumage, on birds. They are the outstanding characteristic that distinguishes the Class Aves from all other living groups. Other Theropoda also had feathers.
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Cladogram showing relationships of extant members of the Sauria. Numbered items are:
Nile Crocodile
