Reptilie Plan: Reptilie Rise of the reptiles Permian reptiles Reptilie

Phylogenetics and modern definition[edit]
By the early 21st century, vertebrate paleontologists were beginning to adopt phylogenetic taxonomy, in which all groups are defined in such a way as to be monophyletic; that is, groups which include all descendants of a particular ancestor. The reptiles as historically defined are paraphyletic, since they exclude both birds and mammals. These respectively evolved from dinosaurs and from early therapsids, which were both traditionally called reptiles.^[18] Birds are more closely related to crocodilians than the latter are to the rest of extant reptiles. Colin Tudge wrote:
Mammals are a clade, and therefore the cladists are happy to acknowledge the traditional taxon Mammalia; and birds, too, are a clade, universally ascribed to the formal taxon Aves. Mammalia and Aves are, in fact, subclades within the grand clade of the Amniota. But the traditional class Reptilia is not a clade. It is just a section of the clade Amniota: the section that is left after the Mammalia and Aves have been hived off. It cannot be defined by synapomorphies, as is the proper way. Instead, it is defined by a combination of the features it has and the features it lacks: reptiles are the amniotes that lack fur or feathers. At best, the cladists suggest, we could say that the traditional Reptilia are 'non-avian, non-mammalian amniotes'.^[14]
Despite the early proposals for replacing the paraphyletic Reptilia with a monophyletic Sauropsida, which includes birds, that term was never adopted widely or, when it was, was not applied consistently.^[19]

Bearded dragon (pogona) skeleton on display at the Museum of Osteology
When Sauropsida was used, it often had the same content or even the same definition as Reptilia. In 1988, Jacques Gauthier proposed a cladistic definition of Reptilia as a monophyletic node-based crown group containing turtles, lizards and snakes, crocodilians, and birds, their common ancestor and all its descendants. While Gauthier's definition was close to the modern consensus, nonetheless, it became considered inadequate because the actual relationship of turtles to other reptiles was not yet well understood at this time.^[19] Major revisions since have included the reassignment of synapsids as non-reptiles, and classification of turtles as diapsids.^[19]
A variety of other definitions were proposed by other scientists in the years following Gauthier's paper. The first such new definition, which attempted to adhere to the standards of the PhyloCode, was published by Modesto and Anderson in 2004. Modesto and Anderson reviewed the many previous definitions and proposed a modified definition, which they intended to retain most traditional content of the group while keeping it stable and monophyletic. They defined Reptilia as all amniotes closer to Lacerta agilis and Crocodylus niloticus than to Homo sapiens. This stem-based definition is equivalent to the more common definition of Sauropsida, which Modesto and Anderson synonymized with Reptilia, since the latter is better known and more frequently used. Unlike most previous definitions of Reptilia, however, Modesto and Anderson's definition includes birds,^[19] as they are within the clade that includes both lizards and crocodiles.^[19]
The cladogram presented here illustrates the "family tree" of reptiles, and follows a simplified version of the relationships found by M.S. Lee, in 2013.^[22] All genetic studies have supported the hypothesis that turtles are diapsids; some have placed turtles within Archosauromorpha,^{[22][23][24][25][26][27]} though a few have recovered turtles as Lepidosauromorpha instead.^[28] The cladogram below used a combination of genetic (molecular) and fossil (morphological) data to obtain its results.^[22]
The origin of the reptiles lies about 310–320 million years ago, in the steaming swamps of the late Carboniferous period, when the first reptiles evolved from advanced reptiliomorphs.^[33]
The oldest known animal that may have been an amniote is Casineria (though it may have been a temnospondyl).^[34][35][36] A series of footprints from the fossil strata of Nova Scotia dated to 315 Ma show typical reptilian toes and imprints of scales.^[37] These tracks are attributed to Hylonomus, the oldest unquestionable reptile known.^[38] It was a small, lizard-like animal, about 20 to 30 centimetres (7.9 to 11.8 in) long, with numerous sharp teeth indicating an insectivorous diet.^[39] Other examples include Westlothiana (for the moment considered a reptiliomorph rather than a true amniote)^[40] and Paleothyris, both of similar build and presumably similar habit.
However, microsaurs have been at times considered true reptiles, so an earlier origin is possible.^[41]