What are the main groups Reptile?

reptiles, also known as class reptiles, Sauropsida class or only sauropsids, are ectotermic ("cold" -i now that this term has now dropped out of fashion) animals covered in scale. There are more than 8,200 reptile types, about 50% more than their relatives, mammals. The reptile is one of the few taxonomic classifications between tetraples that are polyphyletic - which means that the group deviates from the convention of inclusion of all the descendants of the common ancestor. Birds are actually descendants of ancient reptiles, dinosaurs, but are not considered reptiles. If the birds were included in Reptilia, the group would be monophyletic. Amniots raise their embryos using a series of complex membranes. On the other hand, amphibians, ie not amniotic, have simple eggs that must be laid in water.

reptiles and ancestors of mammals, synappers, have been divided by each other very long ago. First known reptile, Hylonomus and the oldest known synappersis, archaeticis lived during the late Carbon period, as ASEven 315 million years ago. Both superficially resembled small lizards, but gave rise to radically different descendants. Synapsides and Sauropsids have since alternated in their domination on Earth, with synapsides from carbon to the extinction of Permian-Triassic about 251 million years ago. Since then, the dinosaurs have begun to evolve and the balance threw themselves back in favor of reptiles. Therefore, this period was called the age of reptiles. After the extinction of the chalk 65 million years ago, all Disian dinosaurs were smoothed and the synapsides in the form of mammals again took over.

There are four live reptile commands: Crocodilia (crocodiles, Alligators, Caimans and Gharials, 23 species), Sphenodontia (Tuatara from New Zealand, 2 species), Squamata (lizards, snakes and amphisbaenides ("Wervowers") species). Tuatara is considered a living relic and is a popular subject of study between phylogenetic and taxonomic communities.

The relationship between reptile groups can be confusing. Testudines have either dividedy very early or are more closely associated with others: we don't know. Turtles lack holes in their skull, which is similar to some of the first reptiles, but may have recently lost their skulls. In addition to Testudin, there are two main groups: Archosaurs, including crocodiles and dinosaurs (including birds coming from dinosaurs) and adhesidosaurs that include everything else.