Evolution of reptiles

Last updated
A fossil of Casineria, which may have been the earliest amniote. Casineria kiddi.jpg
A fossil of Casineria , which may have been the earliest amniote.

Reptiles arose about 320 million years ago [1] during the Carboniferous period. Reptiles, in the traditional sense of the term, are defined as animals that have scales or scutes, lay land-based hard-shelled eggs, and possess ectothermic metabolisms. So defined, the group is paraphyletic, excluding endothermic animals like birds that are descended from early traditionally-defined reptiles. A definition in accordance with phylogenetic nomenclature, which rejects paraphyletic groups, includes birds while excluding mammals and their synapsid ancestors. So defined, Reptilia is identical to Sauropsida.

Contents

Though few reptiles today are apex predators, many examples of apex reptiles have existed in the past. Reptiles have an extremely diverse evolutionary history that has led to biological successes, such as dinosaurs, pterosaurs, plesiosaurs, mosasaurs, and ichthyosaurs.

First reptiles

Rise from water

Reptiles in the traditional sense (green field) are a paraphyletic group comprising all non-avian and non-mammalian amniotes. Traditional Reptilia.png
Reptiles in the traditional sense (green field) are a paraphyletic group comprising all non-avian and non-mammalian amniotes.

Reptiles first arose from earlier tetrapods in the swamps of the late Carboniferous (Early Pennsylvanian - Bashkirian). Increasing evolutionary pressure and the vast untouched niches of the land powered the evolutionary changes in amphibians to gradually become more and more land-based. Environmental selection propelled the development of certain traits, such as a stronger skeletal structure, muscles, and more protective coating (scales) became more favorable; the basic foundation of reptiles were founded. The evolution of lungs and legs are the main transitional steps towards reptiles, but the development of hard-shelled external eggs replacing the amphibious water bound eggs is the defining feature of the class Reptilia and is what allowed these amphibians to fully leave water. Another major difference from amphibians is the increased brain size, more specifically, the enlarged cerebrum and cerebellum. Although their brain size is small when compared to birds and mammals, these enhancements prove vital in hunting strategies of reptiles. The increased size of these two regions of the brain allowed for improved motor skills and an increase in sensory development.

Early reptiles

An early reptile Hylonomus Hylonomus BW.jpg
An early reptile Hylonomus
Mesozoic scene showing typical reptilian megafauna: the dinosaurs Europasaurus holgeri, Iguanodon, and Archaeopteryx perched on the foreground tree stump. Europasaurus holgeri Scene 2.jpg
Mesozoic scene showing typical reptilian megafauna: the dinosaurs Europasaurus holgeri, Iguanodon , and Archaeopteryx perched on the foreground tree stump.

The origin of the reptiles lies about 320–310 million years ago, in the swamps of the late Carboniferous period, when the first reptiles evolved from advanced josemi labyrinthodonts. [2] The oldest known animal that may have been an amniote, a reptile rather than an amphibian, is Casineria [3] [4] (though it has also been argued to be a temnospondyl amphibian). [5]

A series of footprints from the fossil strata of Nova Scotia, dated to 315 million years, show typical reptilian toes and imprints of scales. [6] The tracks are attributed to Hylonomus , the oldest unquestionable reptile known. [7] It was a small, lizard-like animal, about 20 to 30 cm (8–12 in) long, with numerous sharp teeth indicating an insectivorous diet. [8]

Other examples include Westlothiana (sometimes considered a stem-amniote rather than a true amniote) [9] and Paleothyris , both of similar build and presumably similar habit. One of the best known early reptiles is Mesosaurus , a genus from the Early Permian that had returned to water, feeding on fish.

The earliest reptiles were largely overshadowed by bigger labyrinthodont amphibians, such as Cochleosaurus , and remained a small, inconspicuous part of the fauna until after the small ice age at the end of the Carboniferous.

Anapsids, synapsids, diapsids and sauropsids

A = Anapsid, B = Synapsid, C = Diapsid Skull comparison.png
A = Anapsid, B = Synapsid, C = Diapsid

It was traditionally assumed that first reptiles were anapsids, having a solid skull with holes only for the nose, eyes, spinal cord, etc.; [10] the discoveries of synapsid-like openings in the skull roof of the skulls of several members of Parareptilia, including lanthanosuchoids, millerettids, bolosaurids, some nycteroleterids, some procolophonoids and at least some mesosaurs [11] [12] [13] made it more ambiguous and it is currently uncertain whether the ancestral reptile had an anapsid-like or synapsid-like skull. [13] Very soon after the first reptiles appeared, they split into two branches. [14] One branch, Synapsida (including modern mammals), had one opening in the skull roof behind each eye. The other branch, Sauropsida, is itself divided into two main groups. One of them, the aforementioned Parareptilia, contained taxa with anapsid-like skull, as well as taxa with one opening behind each eye (see above). Members of the other group, Diapsida, possessed a hole in their skulls behind each eye, along with a second hole located higher on the skull. The function of the holes in both synapsids and diapsids was to lighten the skull and give room for the jaw muscles to move, allowing for a more powerful bite. [10]

Turtles have been traditionally believed to be surviving anapsids, on the basis of their skull structure. [15] The rationale for this classification was disputed, with some arguing that turtles are diapsids that reverted to this primitive state in order to improve their armor (see Parareptilia). [2] Later morphological phylogenetic studies with this in mind placed turtles firmly within Diapsida. [16] All molecular studies have strongly upheld the placement of turtles within diapsids, most commonly as a sister group to extant archosaurs. [17] [18] [19] [20]

Mammalian evolution

  Tetrapods  

Amphibians

  Amniotes  

Sauropsids

  Synapsids  

Caseasaurs

  Eupelycosaurs  

Sphenacodontids

Therapsids

Mammals

Pelycosaurs

A basic cladogram of the origin of mammals. Important developments in the transition from reptile to mammal were the evolution of warm-bloodedness, of molar occlusion, of the three-ossicle middle ear, of hair, and of mammary glands. By the end of the Triassic, there were many species that looked like modern mammals and, by the Middle Jurassic, the lineages leading to the three extant mammal groups — the monotremes, the marsupials, and the placentals  — had diverged.

Rise of dinosaurs

Permian reptiles

Near the end of the Carboniferous, while the terrestrial reptiliomorph labyrinthodonts were still present, the synapsids evolved the first fully terrestrial large vertebrates, the pelycosaurs such as Edaphosaurus . In the mid-Permian period, the climate turned drier, resulting in a change of fauna: The primitive pelycosaurs were replaced by the more advanced therapsids. [21]

The anapsid reptiles, whose massive skull roofs had no postorbital holes, continued and flourished throughout the Permian. The pareiasaurs reached giant proportions in the late Permian, eventually disappearing at the close of the period. [21]

Late in the period, the diapsid reptiles split into two main lineages, the archosaurs (ancestors of crocodiles and dinosaurs) and the lepidosaurs (predecessors of modern tuataras, lizards, and snakes). Both groups remained lizard-like and relatively small and inconspicuous during the Permian.

The Mesozoic era, the "Age of Reptiles"

The close of the Permian saw the greatest mass extinction known (see the Permian–Triassic extinction event). Most of the earlier anapsid/synapsid megafauna disappeared, being replaced by the archosauromorph diapsids. The archosaurs were characterized by elongated hind legs and an erect pose, the early forms looking somewhat like long-legged crocodiles. The archosaurs became the dominant group during the Triassic period, developing into the well-known dinosaurs and pterosaurs, as well as the pseudosuchians. The Mesozoic is often called the "Age of Reptiles", a phrase coined by the early 19th-century paleontologist Gideon Mantell who recognized the dinosaurs and the ancestors of the crocodilians as the dominant land vertebrates. Some of the dinosaurs were the largest land animals ever to have lived while some of the smaller theropods gave rise to the first birds. [21]

The sister group to Archosauromorpha is Lepidosauromorpha, containing squamates and rhynchocephalians, as well as their fossil relatives. Lepidosauromorpha contained at least one major group of the Mesozoic sea reptiles: the mosasaurs, which emerged during the Cretaceous period. The phylogenetic placement of other main groups of fossil sea reptiles – the sauropterygians and the ichthyosaurs, which evolved in the early Triassic and in the Middle Triassic respectively – is more controversial. Different authors linked these groups either to lepidosauromorphs [22] or to archosauromorphs, [23] [24] [25] and ichthyosaurs were also argued to be diapsids that did not belong to the least inclusive clade containing lepidosauromorphs and archosauromorphs. [26]

The therapsids came under increasing pressure from the dinosaurs in the Jurassic; the mammals and the tritylodontids were the only survivors of the line by the end of the period.

Bird evolution

An Archaeopteryx specimen in Berlin. Archaeopteryx lithographica (Berlin specimen).jpg
An Archaeopteryx specimen in Berlin.

The main points to the transition from reptile to bird are the evolution from scales to feathers, the evolution of the beak (although independently evolved in other organisms), the hallofication of bones, development of flight, and warm-bloodedness.

The evolution of birds is thought to have begun in the Jurassic Period, with the earliest birds derived from theropod dinosaurs. Birds are categorized as a biological class, Aves. The earliest known species in Aves is Archaeopteryx lithographica , from the Late Jurassic period. Modern phylogenetics place birds in the dinosaur clade Theropoda. According to the current consensus, Aves and Crocodilia are the sole living members of an unranked clade, the Archosauria.

Coelurosaurs

Tyrannosauroids

Compsognathids

Maniraptoriformes

Ornithomimosaurs

Maniraptora

Ornitholestes

Therizinosauroids

Alvarezsaurids

Oviraptorosaurs

Paraves

Avialae (birds and their closest relatives)

Deinonychosaurs

Troodontids

Dromaeosaurs

Simplified cladogram from Senter (2007). [27]

Demise of the dinosaurs

The close of the Cretaceous period saw the demise of the Mesozoic era reptilian megafauna. Along with massive amount of volcanic activity at the time, the meteor impact that created the Cretaceous–Paleogene boundary is accepted as the main cause for this mass extinction event. Of the large marine reptiles, only sea turtles are left, and, of the dinosaurs, only the small feathered theropods survived in the form of birds. The end of the “Age of Reptiles” led to the “Age of Mammals”. Despite the change in phrasing, reptile diversification continued throughout the Cenozoic. Today, squamates make up the majority of extant reptiles today (over 90%). [28] There are approximately 9,766 extant species of reptiles, [28] compared with 5,400 species of mammals, so the number of reptilian species (without birds) is nearly twice the number of mammals.

Role reversal

After the Cretaceous–Paleogene extinction event wiped out all of the non-avian dinosaurs (birds are generally regarded as the surviving dinosaurs) and several mammalian groups, placental and marsupial mammals diversified into many new forms and ecological niches throughout the Paleogene and Neogene eras. Some reached enormous sizes and almost as wide a variation as the dinosaurs once did. Nevertheless, mammalian megafauna never quite reached the skyscraper heights of some sauropods.

Nonetheless, large reptiles still composed important megafaunal components, such as giant tortoises, [29] [30] large crocodilians and, more locally, large varanids.

The four orders of Reptilia

Testudines

Testudines, or turtles, may have evolved from anaspids, but their exact origin is unknown and heavily debated. Fossils date back to around 220 million years ago and share remarkably similar characteristics. These first turtles retain the same body plan as do all modern testudines and are mostly herbivorous, with some feeding exclusively on small marine organisms. The trade-mark shell is believed to have evolved from extensions from their backbone and widened ribs that fused together. This is supported by the fossil of Odontochelys semitestacea, which has an incomplete shell originating from the ribs and back bone. This species also had teeth with its beak, giving more support to it being a transitional fossil, although this claim is still controversial. This shell evolved to protect against predators, but also slows down the land-based species by a great amount. This has caused many species to go extinct in recent times. Because of alien species out-competing them for food and the inability to escape from humans, there are many endangered species in this order.

Sphenodontia

Sphenodontians arose in the mid Triassic and now consists of a single genus, tuatara, which comprises two endangered species that live on New Zealand and some of its minor surrounding islands. Their evolutionary history is filled with many species. [31] Recent paleogenetic discoveries show that tuataras are prone to quick speciation.

Squamata

The most recent order of reptiles, squamates, [32] are recognized by having a movable quadrate bone (giving them upper-jaw movement), possessing horny scales and hemipenes. They originate from the early Jurassic and are made up of the three suborders Lacertilia (paraphyletic), Serpentes, and Amphisbaenia. Although they are the most recent order, squamates contain more species than any of the other reptilian orders. Squamates are a monophyletic group included, with the Sphenodontia (e.g. tuataras), in the Lepidosauria. The latter superorder, together with some extinct animals like the plesiosaurs, constitute the Lepidosauromorpha, the sister infraclass to the group, the Archosauromorpha, that contains crocodiles, turtles, and birds. Although squamate fossils first appear in the early Jurassic, mitochondrial phylogenetics suggests that they evolved in the late Permian. Most evolutionary relationships within the squamates are not yet completely worked out, with the relationship of snakes to other groups being most problematic. From morphological data, Iguanid lizards have been thought to have diverged from other squamates very early, but recent molecular phylogenies, both from mitochondrial and nuclear DNA, do not support this early divergence. [33] Because snakes have a faster molecular clock than other squamates, [33] and there are few early snake and snake ancestor fossils, [34] it is difficult to resolve the relationship between snakes and other squamate groups.

Crocodilia

The first organisms that showed similar characteristics of Crocodilians [35] were the Crurotarsi, who appeared during the early Triassic 250 million years ago. This quickly gave rise to the Eusuchia clade 220 million years ago, which would eventually lead to the order of Crocodilians, the first of which arose about 85 million years ago during the late Cretaceous. The earliest fossil evidence of eusuchians is of the genus Isisfordia . Early species mainly fed on fish and vegetation. They were land-based, most having long legs (when compared to modern crocodiles) and many were bipedal. As diversification increased, many apex predators arose, all of which are now extinct. Modern Crocodilia arose through specific evolutionary traits. The complete loss of bipedalism was traded for a generally low quadrupedal stance for an easy and less noticeable entrance to bodies of water. The shape of the skull/jaw changed to allow more grasp along with upward-pointing nostrils and eyes. Mimicry is evident, as the backs of all crocodilia resemble some type of floating log and their general color scheme of brown and green mimics moss or wood. Their tail also took on a paddle shape to increase swimming speed. The only remaining groups [36] of this order are the alligators, caimans, crocodiles, gharials, and false gharials.

Related Research Articles

<span class="mw-page-title-main">Reptile</span> Group of animals including lepidosaurs, testudines, and archosaurs

Reptiles, as commonly defined, are a group of tetrapods with an ectothermic ('cold-blooded') metabolism and amniotic development. Living reptiles comprise four orders: Testudines (turtles), Crocodilia (crocodilians), Squamata, and Rhynchocephalia. As of May 2023, about 12,000 living species of reptiles are listed in the Reptile Database. The study of the traditional reptile orders, customarily in combination with the study of modern amphibians, is called herpetology.

<span class="mw-page-title-main">Anapsid</span> Subclass of reptiles

An anapsid is an amniote whose skull lacks one or more skull openings near the temples. Traditionally, the Anapsida are the most primitive subclass of amniotes, the ancestral stock from which Synapsida and Diapsida evolved, making anapsids paraphyletic. It is however doubtful that all anapsids lack temporal fenestra as a primitive trait, and that all the groups traditionally seen as anapsids truly lacked fenestra.

<span class="mw-page-title-main">Synapsid</span> Clade of tetrapods

Synapsids are one of the two major clades of vertebrate animals in the group Amniota, the other being the sauropsids. The synapsids were the dominant land animals in the late Paleozoic and early Mesozoic, but the only group that survived into the Cenozoic are mammals. Unlike other amniotes, synapsids have a single temporal fenestra, an opening low in the skull roof behind each eye orbit, leaving a bony arch beneath each; this accounts for their name. The distinctive temporal fenestra developed about 318 million years ago during the Late Carboniferous period, when synapsids and sauropsids diverged, but was subsequently merged with the orbit in early mammals.

<span class="mw-page-title-main">Amniote</span> Clade of tetrapods including reptiles, birds and mammals

Amniotes are tetrapod vertebrate animals belonging to the clade Amniota, a large group that comprises the vast majority of living terrestrial and semiaquatic vertebrates. Amniotes evolved from amphibian ancestors during the Carboniferous period and further diverged into two groups, namely the sauropsids and synapsids. They are distinguished from the other living tetrapod clade — the non-amniote lissamphibians — by the development of three extraembryonic membranes, thicker and keratinized skin, and costal respiration.

<span class="mw-page-title-main">Lepidosauria</span> Superorder of reptiles

The Lepidosauria is a subclass or superorder of reptiles, containing the orders Squamata and Rhynchocephalia. Squamata includes lizards and snakes. Squamata contains over 9,000 species, making it by far the most species-rich and diverse order of non-avian reptiles in the present day. Rhynchocephalia was a formerly widespread and diverse group of reptiles in the Mesozoic Era. However, it is represented by only one living species: the tuatara, a superficially lizard-like reptile native to New Zealand.

<span class="mw-page-title-main">Vertebrate paleontology</span> Scientific study of prehistoric vertebrates

Vertebrate paleontology is the subfield of paleontology that seeks to discover, through the study of fossilized remains, the behavior, reproduction and appearance of extinct vertebrates. It also tries to connect, by using the evolutionary timeline, the animals of the past and their modern-day relatives.

<span class="mw-page-title-main">Sauria</span> Clade of reptiles

Sauria is the clade containing the most recent common ancestor of Archosauria and Lepidosauria, and all its descendants. Since most molecular phylogenies recover turtles as more closely related to archosaurs than to lepidosaurs as part of Archelosauria, Sauria can be considered the crown group of diapsids, or reptiles in general. Depending on the systematics, Sauria includes all modern reptiles or most of them as well as various extinct groups.

<span class="mw-page-title-main">Diapsid</span> Clade of amniote tetrapods with two holes in each side of their skulls

Diapsids are a clade of sauropsids, distinguished from more primitive eureptiles by the presence of two holes, known as temporal fenestrae, in each side of their skulls. The group first appeared about three hundred million years ago during the late Carboniferous period. All diapsids other than the most primitive ones in the clade Araeoscelidia are sometimes placed into the clade Neodiapsida. The diapsids are extremely diverse, and include birds and all modern reptile groups, including turtles, which were historically thought to lie outside the group. Although some diapsids have lost either one hole (lizards), or both holes, or have a heavily restructured skull, they are still classified as diapsids based on their ancestry. At least 17,084 species of diapsid animals are extant: 9,159 birds, and 7,925 snakes, lizards, tuatara, turtles, and crocodiles.

<span class="mw-page-title-main">Sauropsida</span> Taxonomic clade

Sauropsida is a clade of amniotes, broadly equivalent to the class Reptilia, though typically used in a broader sense to include both extinct stem-group relatives of modern reptiles, as well as birds. The most popular definition states that Sauropsida is the sibling taxon to Synapsida, the other clade of amniotes which includes mammals as its only modern representatives. Although early synapsids have historically been referred to as "mammal-like reptiles", all synapsids are more closely related to mammals than to any modern reptile. Sauropsids, on the other hand, include all amniotes more closely related to modern reptiles than to mammals. This includes Aves (birds), which are now recognized as a subgroup of archosaurian reptiles despite originally being named as a separate class in Linnaean taxonomy.

<span class="mw-page-title-main">Archosaur</span> Group of diapsids broadly classified as reptiles

Archosauria is a clade of diapsid sauropsid tetrapods, with birds and crocodilians being the only living representatives. Archosaurs are broadly classified as reptiles, in the cladistic sense of the term, which includes birds. Extinct archosaurs include non-avian dinosaurs, pterosaurs and extinct relatives of crocodilians. Modern paleontologists define Archosauria as a crown group that includes the most recent common ancestor of living birds and crocodilians, and all of its descendants. The base of Archosauria splits into two clades: Pseudosuchia, which includes crocodilians and their extinct relatives; and Avemetatarsalia, which includes birds and their extinct relatives.

The quadratojugal is a skull bone present in many vertebrates, including some living reptiles and amphibians.

<span class="mw-page-title-main">Mesosaur</span> Extinct family of reptiles

Mesosaurs were a group of small aquatic reptiles that lived during the early Permian period (Cisuralian), roughly 299 to 270 million years ago. Mesosaurs were the first known aquatic reptiles, having apparently returned to an aquatic lifestyle from more terrestrial ancestors. It is uncertain which and how many terrestrial traits these ancestors displayed; recent research cannot establish with confidence if the first amniotes were fully terrestrial, or only amphibious. Most authors consider mesosaurs to have been aquatic, although adult animals may have been amphibious, rather than completely aquatic, as indicated by their moderate skeletal adaptations to a semiaquatic lifestyle. Similarly, their affinities are uncertain; they may have been among the most basal sauropsids or among the most basal parareptiles.

<span class="mw-page-title-main">Archosauromorpha</span> Infraclass of reptiles

Archosauromorpha is a clade of diapsid reptiles containing all reptiles more closely related to archosaurs rather than lepidosaurs. Archosauromorphs first appeared during the late Middle Permian or Late Permian, though they became much more common and diverse during the Triassic period.

<span class="mw-page-title-main">Neodiapsida</span> Clade of reptiles

Neodiapsida is a clade, or major branch, of the reptilian family tree, typically defined as including all diapsids apart from some early primitive types known as the araeoscelidians. Modern reptiles and birds belong to the neodiapsid subclade Sauria.

<span class="mw-page-title-main">Parareptilia</span> Subclass of reptiles

Parareptilia ("near-reptiles") is a subclass or clade of basal sauropsids/reptiles, typically considered the sister taxon to Eureptilia. Parareptiles first arose near the end of the Carboniferous period and achieved their highest diversity during the Permian period. Several ecological innovations were first accomplished by parareptiles among reptiles. These include the first reptiles to return to marine ecosystems (mesosaurs), the first bipedal reptiles, the first reptiles with advanced hearing systems, and the first large herbivorous reptiles. The only parareptiles to survive into the Triassic period were the procolophonoids, a group of small generalists, omnivores, and herbivores. The largest family of procolophonoids, the procolophonids, rediversified in the Triassic, but subsequently declined and became extinct by the end of the period.

<span class="mw-page-title-main">Procolophonia</span> Extinct suborder of reptiles

Procolophonia is an extinct suborder (clade) of herbivorous reptiles that lived from the Middle Permian till the end of the Triassic period. They were originally included as a suborder of the Cotylosauria but are now considered a clade of Parareptilia. They are closely related to other generally lizard-like Permian reptiles such as the Millerettidae, Bolosauridae, Acleistorhinidae, and Lanthanosuchidae, all of which are included under the Anapsida or "Parareptiles".

<span class="mw-page-title-main">Temporal fenestra</span> Opening in the skull behind the orbit in some animals

Temporal fenestrae are openings in the temporal region of the skull of some amniotes, behind the orbit. These openings have historically been used to track the evolution and affinities of reptiles. Temporal fenestrae are commonly seen in the fossilized skulls of dinosaurs and other sauropsids. The major reptile group Diapsida, for example, is defined by the presence of two temporal fenestrae on each side of the skull. The infratemporal fenestra, also called the lateral temporal fenestra or lower temporal fenestra, is the lower of the two and is exposed primarily in lateral (side) view.

<i>Eunotosaurus</i> Extinct genus of reptiles

Eunotosaurus is an extinct genus of amniote, possibly a close relative of turtles. Eunotosaurus lived in the late Middle Permian and fossils can be found in the Karoo Supergroup of South Africa. Eunotosaurus resided in the swamps of southern Africa. Its ribs were wide and flat, forming broad plates similar to a primitive turtle shell, and the vertebrae were nearly identical to those of some turtles. Accordingly, it is often considered as a possible transitional fossil between turtles and their prehistoric ancestors. However, it is possible that these turtle-like features evolved independently of the same features in turtles, since other anatomical studies and phylogenetic analyses suggest that Eunotosaurus may instead have been a parareptile, an early-diverging neodiapsid unrelated to turtles, or a synapsid.

<span class="mw-page-title-main">Pantestudines</span> Clade of reptiles

Pantestudines or Pan-Testudines is the group of all reptiles more closely related to turtles than to any other living animal. It includes both modern turtles and all of their extinct relatives. Pantestudines with a complete shell are placed in the clade Testudinata.

<i>Pappochelys</i> Extinct genus of reptiles

Pappochelys is an extinct genus of diapsid reptile possibly related to turtles. The genus contains only one species, Pappochelys rosinae, from the Middle Triassic of Germany, which was named by paleontologists Rainer Schoch and Hans-Dieter Sues in 2015. The discovery of Pappochelys provides strong support for the placement of turtles within Diapsida, a hypothesis that has long been suggested by molecular data, but never previously by the fossil record. It is morphologically intermediate between the definite stem-turtle Odontochelys from the Late Triassic of China and Eunotosaurus, a reptile from the Middle Permian of South Africa.

References

  1. ↑ "Reptile Evolution". Biology LibreTexts. LibreTexts. 15 August 2021. Retrieved 13 December 2023.
  2. 1 2 Laurin, M.; Reisz, R. R. (1995). "A reevaluation of early amniote phylogeny". Zoological Journal of the Linnean Society . 113 (2): 165–223. doi:10.1111/j.1096-3642.1995.tb00932.x. S2CID   29661691. (abstract)
  3. ↑ Paton, R. L.; Paton, T. R.; Clack, J. A. (1999). "An amniote-like skeleton from the Early Carboniferous of Scotland". Nature . 398 (6727): 508–513. Bibcode:1999Natur.398..508P. doi:10.1038/19071. S2CID   204992355.
  4. ↑ Monastersky, R. (1999) Out of the Swamps, How early vertebrates established a foothold—with all 10 toes—on land. Science News, Vol. 155, No. 21, p. 328. article
  5. ↑ Chapter 6: "Walking with early tetrapods: evolution of the postcranial skeleton and the phylogenetic affinities of the Temnospondyli (Vertebrata: Tetrapoda)." In: Kat Pawley (2006). "The postcranial skeleton of temnospondyls (Tetrapoda: temnospondyli)." PhD Thesis. La Trobe University, Melbourne.
  6. ↑ Falcon-Lang, H.J.; Benton, M.J.; Stimson, M. (2007). "Ecology of early reptiles inferred from Lower Pennsylvanian trackways". Journal of the Geological Society. 164 (6): 1113–1118. doi:10.1144/0016-76492007-015. S2CID   140568921.
  7. ↑ "Earliest Evidence For Reptiles". Sflorg.com. 2007-10-17. Archived from the original on 2011-07-16. Retrieved 2010-03-16.
  8. ↑ Palmer, D., ed. (1999). The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals. London: Marshall Editions. p. 62. ISBN   1-84028-152-9.
  9. ↑ Ruta, M.; Coates, M.I.; Quicke, D.L.J. (2003). "Early tetrapod relationships revisited" (PDF). Biological Reviews. 78 (2): 251–345. doi:10.1017/S1464793102006103. PMID   12803423. S2CID   31298396. Archived from the original (PDF) on 2008-05-22. Retrieved 2011-01-23.
  10. 1 2 Romer, A.S. & T.S. Parsons. 1977. The Vertebrate Body. 5th ed. Saunders, Philadelphia. (6th ed. 1985)
  11. ↑ Juan C. Cisneros; Ross Damiani; Cesar Schultz; Átila da Rosa; Cibele Schwanke; Leopoldo W. Neto; Pedro L. P. Aurélio (2004). "A procolophonoid reptile with temporal fenestration from the Middle Triassic of Brazil". Proceedings of the Royal Society B: Biological Sciences. 271 (1547): 1541–1546. doi:10.1098/rspb.2004.2748. PMC   1691751 . PMID   15306328.
  12. ↑ Linda A. Tsuji; Johannes Müller (2009). "Assembling the history of the Parareptilia: phylogeny, diversification, and a new definition of the clade". Fossil Record. 12 (1): 71–81. doi: 10.1002/mmng.200800011 .
  13. 1 2 Graciela Piñeiro; Jorge Ferigolo; Alejandro Ramos; Michel Laurin (2012). "Cranial morphology of the Early Permian mesosaurid Mesosaurus tenuidens and the evolution of the lower temporal fenestration reassessed". Comptes Rendus Palevol. 11 (5): 379–391. doi:10.1016/j.crpv.2012.02.001.
  14. ↑ Van Tuninen, M.; Hadly, E.A. (2004). "Error in Estimation of Rate and Time Inferred from the Early Amniote Fossil Record and Avian Molecular Clocks" (PDF). Journal of Molecular Biology. 59 (2): 267–276. Bibcode:2004JMolE..59..267V. doi:10.1007/s00239-004-2624-9. PMID   15486700. S2CID   25065918. Archived from the original (PDF) on 2011-06-28.
  15. ↑ Benton, M. J. (2000). Vertebrate Palaeontology (2nd ed.). London: Blackwell Science Ltd. ISBN   0-632-05614-2., 3rd ed. 2004 ISBN   0-632-05637-1
  16. ↑ Rieppel O, DeBraga M (1996). "Turtles as diapsid reptiles" (PDF). Nature. 384 (6608): 453–5. Bibcode:1996Natur.384..453R. doi:10.1038/384453a0. S2CID   4264378.
  17. ↑ Zardoya, R.; Meyer, A. (1998). "Complete mitochondrial genome suggests diapsid affinities of turtles" (PDF). Proc Natl Acad Sci U S A . 95 (24): 14226–14231. Bibcode:1998PNAS...9514226Z. doi: 10.1073/pnas.95.24.14226 . ISSN   0027-8424. PMC   24355 . PMID   9826682.
  18. ↑ Iwabe, N.; Hara, Y.; Kumazawa, Y.; Shibamoto, K.; Saito, Y.; Miyata, T.; Katoh, K. (2004-12-29). "Sister group relationship of turtles to the bird-crocodilian clade revealed by nuclear DNA-coded proteins". Molecular Biology and Evolution . 22 (4): 810–813. doi: 10.1093/molbev/msi075 . PMID   15625185.
  19. ↑ Roos, Jonas; Aggarwal, Ramesh K.; Janke, Axel (Nov 2007). "Extended mitogenomic phylogenetic analyses yield new insight into crocodylian evolution and their survival of the Cretaceous–Tertiary boundary". Molecular Phylogenetics and Evolution . 45 (2): 663–673. doi:10.1016/j.ympev.2007.06.018. PMID   17719245.
  20. ↑ Guillette, Y.; Braun, E. L.; Guillette, L. J. Jr; Iguchi, T. (2010-03-17). "From reptilian phylogenomics to reptilian genomes: analyses of c-Jun and DJ-1 proto-oncogenes". Cytogenetic and Genome Research. 127 (2–4): 79–93. doi:10.1159/000297715. PMID   20234127. S2CID   12116018.
  21. 1 2 3 Colbert, E.H. & Morales, M. (2001): Colbert's Evolution of the Vertebrates: A History of the Backboned Animals Through Time . 4th edition. John Wiley & Sons, Inc, New York — ISBN   978-0-471-38461-8.
  22. ↑ Gauthier J. A. (1994): The diversification of the amniotes. In: D. R. Prothero and R. M. Schoch (ed.) Major Features of Vertebrate Evolution: 129-159. Knoxville, Tennessee: The Paleontological Society.
  23. ↑ John W. Merck (1997). "A phylogenetic analysis of the euryapsid reptiles". Journal of Vertebrate Paleontology. 17 (Supplement to 3): 65A. doi:10.1080/02724634.1997.10011028.
  24. ↑ Sean Modesto; Robert Reisz; Diane Scott (2011). "A neodiapsid reptile from the Lower Permian of Oklahoma". Society of Vertebrate Paleontology 71st Annual Meeting Program and Abstracts: 160.
  25. ↑ "GEOL 331/BSCI 333 Tetrapod Paleontology". Geol.umd.edu.
  26. ↑ Ryosuke Motani; Nachio Minoura; Tatsuro Ando (1998). "Ichthyosaurian relationships illuminated by new primitive skeletons from Japan". Nature. 393 (6682): 255–257. Bibcode:1998Natur.393..255M. doi:10.1038/30473. S2CID   4416186.
  27. ↑ Phil Senter (2007). "A new look at the phylogeny of coelurosauria (Dinosauria: Theropoda)". Journal of Systematic Palaeontology. 5 (4): 429–463. doi:10.1017/S1477201907002143. S2CID   83726237.
  28. 1 2 "The Reptile Database" . Retrieved 1 February 2012.
  29. ↑ Hansen, D. M.; Donlan, C. J.; Griffiths, C. J.; Campbell, K. J. (April 2010). "Ecological history and latent conservation potential: large and giant tortoises as a model for taxon substitutions" (PDF). Ecography . Wiley. 33 (2): 272–284. doi:10.1111/j.1600-0587.2010.06305.x. Archived from the original (PDF) on 2011-07-24. Retrieved 2011-02-26.
  30. ↑ Cione, A. L.; Tonni, E. P.; Soibelzon, L. (2003). "The Broken Zig-Zag: Late Cenozoic large mammal and tortoise extinction in South America". Rev. Mus. Argentino Cienc. Nat. N.S. 5 (1): 1–19. doi: 10.22179/REVMACN.5.26 . ISSN   1514-5158.
  31. ↑ "Ancient, Lizard-Like Reptile Discovered". Archived from the original on 2017-09-25. Retrieved 2015-04-18.
  32. ↑ Reeder, Tod W.; Townsend, Ted M.; Mulcahy, Daniel G.; Noonan, Brice P.; Wood, Perry L.; Sites, Jack W.; Wiens, John J. (2015). "Integrated Analyses Resolve Conflicts over Squamate Reptile Phylogeny and Reveal Unexpected Placements for Fossil Taxa". PLOS ONE. 10 (3): e0118199. Bibcode:2015PLoSO..1018199R. doi: 10.1371/journal.pone.0118199 . PMC   4372529 . PMID   25803280.
  33. 1 2 Kumazawa, Yoshinori (2007). "Mitochondrial genomes from major lizard families suggest their phylogenetic relationships and ancient radiations". Gene. 388 (1–2): 19–26. doi:10.1016/j.gene.2006.09.026. PMID   17118581.
  34. ↑ "Lizards & Snakes Alive!". American Museum of Natural History. Archived from the original on 2008-01-28. Retrieved 2007-12-25.
  35. ↑ "Crocodilians: Natural History and Conservation - Crocodiles, Caimans, Alligators, Gharials". Crocodilian.com. Retrieved 2022-04-12.
  36. ↑ "Alligator vs Crocodile - Differences Explained (With Videos and Pictures)". Diffen.com.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.