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For other uses, see Reptile (disambiguation). Reptile_sentence_0



Temporal range: PennsylvanianPresent, 312–0 Ma PreꞒ O S D C P T J K Pg NReptile_header_cell_0_0_0

Scientific classification ReptiliaReptile_header_cell_0_1_0
Kingdom:Reptile_cell_0_2_0 AnimaliaReptile_cell_0_2_1
Phylum:Reptile_cell_0_3_0 ChordataReptile_cell_0_3_1
Clade:Reptile_cell_0_4_0 SauropsidaReptile_cell_0_4_1
Class:Reptile_cell_0_5_0 Reptilia

Laurenti, 1768Reptile_cell_0_5_1

Extant groupsReptile_header_cell_0_6_0

Reptiles are tetrapod animals in the class Reptilia /rɛpˈtɪliə/, a paraphyletic grouping comprising all amniotes except mammals and birds. Reptile_sentence_1

Properly, reptiles and birds are grouped together in the monophyletic group known as sauropsids. Reptile_sentence_2

The class Reptilia comprises turtles, crocodilians, snakes, amphisbaenians, lizards, tuatara, and their extinct relatives. Reptile_sentence_3

The study of the traditional reptile orders, historically combined with that of modern amphibians, is called herpetology. Reptile_sentence_4

The earliest known proto-reptiles originated around 312 million years ago during the Carboniferous period, having evolved from advanced reptiliomorph tetrapods that became increasingly adapted to life on dry land. Reptile_sentence_5

Some early examples include the lizard-like Hylonomus and Casineria. Reptile_sentence_6

In addition to the living reptiles, there are many diverse groups that are now extinct, in some cases due to mass extinction events. Reptile_sentence_7

In particular, the Cretaceous–Paleogene extinction event wiped out the pterosaurs, plesiosaurs, ornithischians, and sauropods, alongside many species of theropods, crocodyliforms, and squamates (e.g., mosasaurs). Reptile_sentence_8

Modern reptiles inhabit all the continents except Antarctica. Reptile_sentence_9

Several living subgroups are recognized: Testudines (turtles and tortoises), 360 species; Rhynchocephalia (tuatara from New Zealand), 1 species; Squamata (lizards, snakes, and worm lizards), about 10,954 species; and Crocodilia (crocodiles, gharials, caimans, and alligators), 27 species. Reptile_sentence_10

Reptiles are tetrapod vertebrates, creatures that either have four limbs or, like snakes, are descended from four-limbed ancestors. Reptile_sentence_11

Unlike amphibians, reptiles do not have an aquatic larval stage. Reptile_sentence_12

Most reptiles are oviparous, although several species of squamates are viviparous, as were some extinct aquatic clades – the fetus develops within the mother, using a (non-mammalian) placenta rather than contained in an eggshell. Reptile_sentence_13

As amniotes, reptile eggs are surrounded by membranes for protection and transport, which adapt them to reproduction on dry land. Reptile_sentence_14

Many of the viviparous species feed their fetuses through various forms of placenta analogous to those of mammals, with some providing initial care for their hatchlings. Reptile_sentence_15

Extant reptiles range in size from a tiny gecko, Sphaerodactylus ariasae, which can grow up to 17 mm (0.7 in) to the saltwater crocodile, Crocodylus porosus, which can reach 6 m (19.7 ft) in length and weigh over 1,000 kg (2,200 lb). Reptile_sentence_16

Classification Reptile_section_0

See also: List of reptiles Reptile_sentence_17

Research history Reptile_section_1

See also: Skull roof Reptile_sentence_18

In the 13th century the category of reptile was recognized in Europe as consisting of a miscellany of egg-laying creatures, including "snakes, various fantastic monsters, lizards, assorted amphibians, and worms", as recorded by Vincent of Beauvais in his Mirror of Nature. Reptile_sentence_19

In the 18th century, the reptiles were, from the outset of classification, grouped with the amphibians. Reptile_sentence_20

Linnaeus, working from species-poor Sweden, where the common adder and grass snake are often found hunting in water, included all reptiles and amphibians in class "III – Amphibia" in his Systema Naturæ. Reptile_sentence_21

The terms reptile and amphibian were largely interchangeable, reptile (from Latin repere, 'to creep') being preferred by the French. Reptile_sentence_22

Josephus Nicolaus Laurenti was the first to formally use the term Reptilia for an expanded selection of reptiles and amphibians basically similar to that of Linnaeus. Reptile_sentence_23

Today, the two groups are still commonly treated under the single heading herpetology. Reptile_sentence_24

It was not until the beginning of the 19th century that it became clear that reptiles and amphibians are, in fact, quite different animals, and Pierre André Latreille erected the class Batracia (1825) for the latter, dividing the tetrapods into the four familiar classes of reptiles, amphibians, birds, and mammals. Reptile_sentence_25

The British anatomist Thomas Henry Huxley made Latreille's definition popular and, together with Richard Owen, expanded Reptilia to include the various fossil "antediluvian monsters", including dinosaurs and the mammal-like (synapsid) Dicynodon he helped describe. Reptile_sentence_26

This was not the only possible classification scheme: In the Hunterian lectures delivered at the Royal College of Surgeons in 1863, Huxley grouped the vertebrates into mammals, sauroids, and ichthyoids (the latter containing the fishes and amphibians). Reptile_sentence_27

He subsequently proposed the names of Sauropsida and Ichthyopsida for the latter two groups. Reptile_sentence_28

In 1866, Haeckel demonstrated that vertebrates could be divided based on their reproductive strategies, and that reptiles, birds, and mammals were united by the amniotic egg. Reptile_sentence_29

The terms Sauropsida ('lizard faces') and Theropsida ('beast faces') were used again in 1916 by E.S. Reptile_sentence_30 Goodrich to distinguish between lizards, birds, and their relatives on the one hand (Sauropsida) and mammals and their extinct relatives (Theropsida) on the other. Reptile_sentence_31

Goodrich supported this division by the nature of the hearts and blood vessels in each group, and other features, such as the structure of the forebrain. Reptile_sentence_32

According to Goodrich, both lineages evolved from an earlier stem group, Protosauria ("first lizards") in which he included some animals today considered reptile-like amphibians, as well as early reptiles. Reptile_sentence_33

In 1956, D.M.S. Reptile_sentence_34 Watson observed that the first two groups diverged very early in reptilian history, so he divided Goodrich's Protosauria between them. Reptile_sentence_35

He also reinterpreted Sauropsida and Theropsida to exclude birds and mammals, respectively. Reptile_sentence_36

Thus his Sauropsida included Procolophonia, Eosuchia, Millerosauria, Chelonia (turtles), Squamata (lizards and snakes), Rhynchocephalia, Crocodilia, "thecodonts" (paraphyletic basal Archosauria), non- dinosaurs, pterosaurs, ichthyosaurs, and sauropterygians. Reptile_sentence_37

In the late 19th century, a number of definitions of Reptilia were offered. Reptile_sentence_38

The traits listed by Lydekker in 1896, for example, include a single occipital condyle, a jaw joint formed by the quadrate and articular bones, and certain characteristics of the vertebrae. Reptile_sentence_39

The animals singled out by these formulations, the amniotes other than the mammals and the birds, are still those considered reptiles today. Reptile_sentence_40

The synapsid/sauropsid division supplemented another approach, one that split the reptiles into four subclasses based on the number and position of temporal fenestrae, openings in the sides of the skull behind the eyes. Reptile_sentence_41

This classification was initiated by Henry Fairfield Osborn and elaborated and made popular by Romer's classic Vertebrate Paleontology. Reptile_sentence_42

Those four subclasses were: Reptile_sentence_43


The composition of Euryapsida was uncertain. Reptile_sentence_44

Ichthyosaurs were, at times, considered to have arisen independently of the other euryapsids, and given the older name Parapsida. Reptile_sentence_45

Parapsida was later discarded as a group for the most part (ichthyosaurs being classified as incertae sedis or with Euryapsida). Reptile_sentence_46

However, four (or three if Euryapsida is merged into Diapsida) subclasses remained more or less universal for non-specialist work throughout the 20th century. Reptile_sentence_47

It has largely been abandoned by recent researchers: In particular, the anapsid condition has been found to occur so variably among unrelated groups that it is not now considered a useful distinction. Reptile_sentence_48

Phylogenetics and modern definition Reptile_section_2

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. Reptile_sentence_49

The reptiles as historically defined are paraphyletic, since they exclude both birds and mammals. Reptile_sentence_50

These respectively evolved from dinosaurs and from early therapsids, which were both traditionally called reptiles. Reptile_sentence_51

Birds are more closely related to crocodilians than the latter are to the rest of extant reptiles. Reptile_sentence_52

Colin Tudge wrote: Reptile_sentence_53

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. Reptile_sentence_54

When Sauropsida was used, it often had the same content or even the same definition as Reptilia. Reptile_sentence_55

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. Reptile_sentence_56

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. Reptile_sentence_57

Major revisions since have included the reassignment of synapsids as non-reptiles, and classification of turtles as diapsids. Reptile_sentence_58

A variety of other definitions were proposed by other scientists in the years following Gauthier's paper. Reptile_sentence_59

The first such new definition, which attempted to adhere to the standards of the PhyloCode, was published by Modesto and Anderson in 2004. Reptile_sentence_60

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. Reptile_sentence_61

They defined Reptilia as all amniotes closer to Lacerta agilis and Crocodylus niloticus than to Homo sapiens. Reptile_sentence_62

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. Reptile_sentence_63

Unlike most previous definitions of Reptilia, however, Modesto and Anderson's definition includes birds, as they are within the clade that includes both lizards and crocodiles. Reptile_sentence_64

Taxonomy Reptile_section_3

See also: List of reptiles and List of snakes Reptile_sentence_65

Classification to order level of the reptiles, after Benton, 2014. Reptile_sentence_66


Phylogeny Reptile_section_4

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. Reptile_sentence_67

All genetic studies have supported the hypothesis that turtles are diapsids; some have placed turtles within archosauriformes, though a few have recovered turtles as lepidosauriformes instead. Reptile_sentence_68

The cladogram below used a combination of genetic (molecular) and fossil (morphological) data to obtain its results. Reptile_sentence_69

The position of turtles Reptile_section_5

The placement of turtles has historically been highly variable. Reptile_sentence_70

Classically, turtles were considered to be related to the primitive anapsid reptiles. Reptile_sentence_71

Molecular work has usually placed turtles within the diapsids. Reptile_sentence_72

As of 2013, three turtle genomes have been sequenced. Reptile_sentence_73

The results place turtles as a sister clade to the archosaurs, the group that includes crocodiles, dinosaurs, and birds. Reptile_sentence_74

However, in their comparative analysis of the timing of organogenesis, Werneburg and Sánchez-Villagra (2009) found support for the hypothesis that turtles belong to a separate clade within Sauropsida, outside the saurian clade altogether. Reptile_sentence_75

Evolutionary history Reptile_section_6

Main article: Evolution of reptiles Reptile_sentence_76

Origin of the reptiles Reptile_section_7

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. Reptile_sentence_77

The oldest known animal that may have been an amniote is Casineria (though it may have been a temnospondyl). Reptile_sentence_78

A series of footprints from the fossil strata of Nova Scotia dated to 315 Ma show typical reptilian toes and imprints of scales. Reptile_sentence_79

These tracks are attributed to Hylonomus, the oldest unquestionable reptile known. Reptile_sentence_80

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. Reptile_sentence_81

Other examples include Westlothiana (for the moment considered a reptiliomorph rather than a true amniote) and Paleothyris, both of similar build and presumably similar habit. Reptile_sentence_82

Rise of the reptiles Reptile_section_8

The earliest amniotes, including stem-reptiles (those amniotes closer to modern reptiles than to mammals), were largely overshadowed by larger stem-tetrapods, such as Cochleosaurus, and remained a small, inconspicuous part of the fauna until the Carboniferous Rainforest Collapse. Reptile_sentence_83

This sudden collapse affected several large groups. Reptile_sentence_84

Primitive tetrapods were particularly devastated, while stem-reptiles fared better, being ecologically adapted to the drier conditions that followed. Reptile_sentence_85

Primitive tetrapods, like modern amphibians, need to return to water to lay eggs; in contrast, amniotes, like modern reptiles – whose eggs possess a shell that allows them to be laid on land – were better adapted to the new conditions. Reptile_sentence_86

Amniotes acquired new niches at a faster rate than before the collapse and at a much faster rate than primitive tetrapods. Reptile_sentence_87

They acquired new feeding strategies including herbivory and carnivory, previously only having been insectivores and piscivores. Reptile_sentence_88

From this point forward, reptiles dominated communities and had a greater diversity than primitive tetrapods, setting the stage for the Mesozoic (known as the Age of Reptiles). Reptile_sentence_89

One of the best known early stem-reptiles is Mesosaurus, a genus from the Early Permian that had returned to water, feeding on fish. Reptile_sentence_90

Anapsids, synapsids, diapsids, and sauropsids Reptile_section_9

It was traditionally assumed that the first reptiles retained an anapsid skull inherited from their ancestors. Reptile_sentence_91

This type of skull has a skull roof with only holes for the nostrils, eyes and a pineal eye. Reptile_sentence_92

The discoveries of synapsid-like openings (see below) in the skull roof of the skulls of several members of Parareptilia (the clade containing most of the amniotes traditionally referred to as "anapsids"), including lanthanosuchoids, millerettids, bolosaurids, some nycteroleterids, some procolophonoids and at least some mesosaurs made it more ambiguous and it's currently uncertain whether the ancestral amniote had an anapsid-like or synapsid-like skull. Reptile_sentence_93

These animals are traditionally referred to as "anapsids", and form a paraphyletic basic stock from which other groups evolved. Reptile_sentence_94

Very shortly after the first amniotes appeared, a lineage called Synapsida split off; this group was characterized by a temporal opening in the skull behind each eye to give room for the jaw muscle to move. Reptile_sentence_95

These are the "mammal-like amniotes", or stem-mammals, that later gave rise to the true mammals. Reptile_sentence_96

Soon after, another group evolved a similar trait, this time with a double opening behind each eye, earning them the name Diapsida ("two arches"). Reptile_sentence_97

The function of the holes in these groups was to lighten the skull and give room for the jaw muscles to move, allowing for a more powerful bite. Reptile_sentence_98

Turtles have been traditionally believed to be surviving parareptiles, on the basis of their anapsid skull structure, which was assumed to be primitive trait. Reptile_sentence_99

The rationale for this classification has been disputed, with some arguing that turtles are diapsids that evolved anapsid skulls in order to improve their armor. Reptile_sentence_100

Later morphological phylogenetic studies with this in mind placed turtles firmly within Diapsida. Reptile_sentence_101

All molecular studies have strongly upheld the placement of turtles within diapsids, most commonly as a sister group to extant archosaurs. Reptile_sentence_102

Permian reptiles Reptile_section_10

With the close of the Carboniferous, the amniotes became the dominant tetrapod fauna. Reptile_sentence_103

While primitive, terrestrial reptiliomorphs still existed, the synapsid amniotes evolved the first truly terrestrial megafauna (giant animals) in the form of pelycosaurs, such as Edaphosaurus and the carnivorous Dimetrodon. Reptile_sentence_104

In the mid-Permian period, the climate became drier, resulting in a change of fauna: The pelycosaurs were replaced by the therapsids. Reptile_sentence_105

The parareptiles, whose massive skull roofs had no postorbital holes, continued and flourished throughout the Permian. Reptile_sentence_106

The pareiasaurian parareptiles reached giant proportions in the late Permian, eventually disappearing at the close of the period (the turtles being possible survivors). Reptile_sentence_107

Early in the period, the modern reptiles, or crown-group reptiles, evolved and split into two main lineages: the Archosauromorpha (forebears of turtles, crocodiles, and dinosaurs) and the Lepidosauromorpha (predecessors of modern lizards and tuataras). Reptile_sentence_108

Both groups remained lizard-like and relatively small and inconspicuous during the Permian. Reptile_sentence_109

Mesozoic reptiles Reptile_section_11

The close of the Permian saw the greatest mass extinction known (see the Permian–Triassic extinction event), an event prolonged by the combination of two or more distinct extinction pulses. Reptile_sentence_110

Most of the earlier parareptile and synapsid megafauna disappeared, being replaced by the true reptiles, particularly archosauromorphs. Reptile_sentence_111

These were characterized by elongated hind legs and an erect pose, the early forms looking somewhat like long-legged crocodiles. Reptile_sentence_112

The archosaurs became the dominant group during the Triassic period, though it took 30 million years before their diversity was as great as the animals that lived in the Permian. Reptile_sentence_113

Archosaurs developed into the well-known dinosaurs and pterosaurs, as well as the ancestors of crocodiles. Reptile_sentence_114

Since reptiles, first rauisuchians and then dinosaurs, dominated the Mesozoic era, the interval is popularly known as the "Age of Reptiles". Reptile_sentence_115

The dinosaurs also developed smaller forms, including the feather-bearing smaller theropods. Reptile_sentence_116

In the Cretaceous period, these gave rise to the first true birds. Reptile_sentence_117

The sister group to Archosauromorpha is Lepidosauromorpha, containing lizards and tuataras, as well as their fossil relatives. Reptile_sentence_118

Lepidosauromorpha contained at least one major group of the Mesozoic sea reptiles: the mosasaurs, which lived during the Cretaceous period. Reptile_sentence_119

The phylogenetic placement of other main groups of fossil sea reptiles – the ichthyopterygians (including ichthyosaurs) and the sauropterygians, which evolved in the early Triassic – is more controversial. Reptile_sentence_120

Different authors linked these groups either to lepidosauromorphs or to archosauromorphs, and ichthyopterygians were also argued to be diapsids that did not belong to the least inclusive clade containing lepidosauromorphs and archosauromorphs. Reptile_sentence_121

Cenozoic reptiles Reptile_section_12

The close of the Cretaceous period saw the demise of the Mesozoic era reptilian megafauna (see the Cretaceous–Paleogene extinction event, also known as K-T extinction event). Reptile_sentence_122

Of the large marine reptiles, only sea turtles were left; and of the non-marine large reptiles, only the semi-aquatic crocodiles and broadly similar choristoderes survived the extinction, with the latter becoming extinct in the Miocene. Reptile_sentence_123

Of the great host of dinosaurs dominating the Mesozoic, only the small beaked birds survived. Reptile_sentence_124

This dramatic extinction pattern at the end of the Mesozoic led into the Cenozoic. Reptile_sentence_125

Mammals and birds filled the empty niches left behind by the reptilian megafauna and, while reptile diversification slowed, bird and mammal diversification took an exponential turn. Reptile_sentence_126

However, reptiles were still important components of the megafauna, particularly in the form of large and giant tortoises. Reptile_sentence_127

After the extinction of most archosaur and marine reptile lines by the end of the Cretaceous, reptile diversification continued throughout the Cenozoic. Reptile_sentence_128

Squamates took a massive hit during the KT-event, only recovering ten million years after it, but they underwent a great radiation event once they recovered, and today squamates make up the majority of living reptiles (> 95%). Reptile_sentence_129

Approximately 10,000 extant species of traditional reptiles are known, with birds adding about 10,000 more, almost twice the number of mammals, represented by about 5,700 living species (excluding domesticated species). Reptile_sentence_130


Species diversity of living reptiles (2013)Reptile_table_caption_1
Reptile groupReptile_header_cell_1_0_0 Described speciesReptile_header_cell_1_0_1 Percent of reptile speciesReptile_header_cell_1_0_2
SquamatesReptile_cell_1_1_0 9193Reptile_cell_1_1_1 96.3%Reptile_cell_1_1_2
- LizardsReptile_cell_1_2_0 5634Reptile_cell_1_2_1 59%Reptile_cell_1_2_2
- SnakesReptile_cell_1_3_0 3378Reptile_cell_1_3_1 35%Reptile_cell_1_3_2
- AmphisbaeniansReptile_cell_1_4_0 181Reptile_cell_1_4_1 2%Reptile_cell_1_4_2
TurtlesReptile_cell_1_5_0 327Reptile_cell_1_5_1 3.4%Reptile_cell_1_5_2
CrocodiliansReptile_cell_1_6_0 25Reptile_cell_1_6_1 0.3%Reptile_cell_1_6_2
RhynchocephaliansReptile_cell_1_7_0 1Reptile_cell_1_7_1 0.01%Reptile_cell_1_7_2
TotalReptile_cell_1_8_0 9546Reptile_cell_1_8_1 100%Reptile_cell_1_8_2

Morphology and physiology Reptile_section_13

Circulation Reptile_section_14

All squamates and turtles have a three-chambered heart consisting of two atria, one variably partitioned ventricle, and two aortas that lead to the systemic circulation. Reptile_sentence_131

The degree of mixing of oxygenated and deoxygenated blood in the three-chambered heart varies depending on the species and physiological state. Reptile_sentence_132

Under different conditions, deoxygenated blood can be shunted back to the body or oxygenated blood can be shunted back to the lungs. Reptile_sentence_133

This variation in blood flow has been hypothesized to allow more effective thermoregulation and longer diving times for aquatic species, but has not been shown to be a fitness advantage. Reptile_sentence_134

For example, Iguana hearts, like the majority of the squamates hearts, are composed of three chambers with two aorta and one ventricle, cardiac involuntary muscles. Reptile_sentence_135

The main structures of the heart are the sinus venosus, the pacemaker, the left atrium, the right atruim, the atrioventricular valve, the cavum venosum, cavum arteriosum, the cavum pulmonale, the muscular ridge, the ventricular ridge, pulmonary veins, and paired aortic arches. Reptile_sentence_136

Some squamate species (e.g., pythons and monitor lizards) have three-chambered hearts that become functionally four-chambered hearts during contraction. Reptile_sentence_137

This is made possible by a muscular ridge that subdivides the ventricle during ventricular diastole and completely divides it during ventricular systole. Reptile_sentence_138

Because of this ridge, some of these squamates are capable of producing ventricular pressure differentials that are equivalent to those seen in mammalian and avian hearts. Reptile_sentence_139

Crocodilians have an anatomically four-chambered heart, similar to birds, but also have two systemic aortas and are therefore capable of bypassing their pulmonary circulation. Reptile_sentence_140

Metabolism Reptile_section_15

Modern non-avian reptiles exhibit some form of cold-bloodedness (i.e. some mix of poikilothermy, ectothermy, and bradymetabolism) so that they have limited physiological means of keeping the body temperature constant and often rely on external sources of heat. Reptile_sentence_141

Due to a less stable core temperature than birds and mammals, reptilian biochemistry requires enzymes capable of maintaining efficiency over a greater range of temperatures than in the case for warm-blooded animals. Reptile_sentence_142

The optimum body temperature range varies with species, but is typically below that of warm-blooded animals; for many lizards, it falls in the 24°–35 °C (75°–95 °F) range, while extreme heat-adapted species, like the American desert iguana Dipsosaurus dorsalis, can have optimal physiological temperatures in the mammalian range, between 35° and 40 °C (95° and 104 °F). Reptile_sentence_143

While the optimum temperature is often encountered when the animal is active, the low basal metabolism makes body temperature drop rapidly when the animal is inactive. Reptile_sentence_144

As in all animals, reptilian muscle action produces heat. Reptile_sentence_145

In large reptiles, like leatherback turtles, the low surface-to-volume ratio allows this metabolically produced heat to keep the animals warmer than their environment even though they do not have a warm-blooded metabolism. Reptile_sentence_146

This form of homeothermy is called gigantothermy; it has been suggested as having been common in large dinosaurs and other extinct large-bodied reptiles. Reptile_sentence_147

The benefit of a low resting metabolism is that it requires far less fuel to sustain bodily functions. Reptile_sentence_148

By using temperature variations in their surroundings, or by remaining cold when they do not need to move, reptiles can save considerable amounts of energy compared to endothermic animals of the same size. Reptile_sentence_149

A crocodile needs from a tenth to a fifth of the food necessary for a lion of the same weight and can live half a year without eating. Reptile_sentence_150

Lower food requirements and adaptive metabolisms allow reptiles to dominate the animal life in regions where net calorie availability is too low to sustain large-bodied mammals and birds. Reptile_sentence_151

It is generally assumed that reptiles are unable to produce the sustained high energy output necessary for long distance chases or flying. Reptile_sentence_152

Higher energetic capacity might have been responsible for the evolution of warm-bloodedness in birds and mammals. Reptile_sentence_153

However, investigation of correlations between active capacity and thermophysiology show a weak relationship. Reptile_sentence_154

Most extant reptiles are carnivores with a sit-and-wait feeding strategy; whether reptiles are cold blooded due to their ecology is not clear. Reptile_sentence_155

Energetic studies on some reptiles have shown active capacities equal to or greater than similar sized warm-blooded animals. Reptile_sentence_156

Respiratory system Reptile_section_16

All reptiles breathe using lungs. Reptile_sentence_157

Aquatic turtles have developed more permeable skin, and some species have modified their cloaca to increase the area for gas exchange. Reptile_sentence_158

Even with these adaptations, breathing is never fully accomplished without lungs. Reptile_sentence_159

Lung ventilation is accomplished differently in each main reptile group. Reptile_sentence_160

In squamates, the lungs are ventilated almost exclusively by the axial musculature. Reptile_sentence_161

This is also the same musculature that is used during locomotion. Reptile_sentence_162

Because of this constraint, most squamates are forced to hold their breath during intense runs. Reptile_sentence_163

Some, however, have found a way around it. Reptile_sentence_164

Varanids, and a few other lizard species, employ buccal pumping as a complement to their normal "axial breathing". Reptile_sentence_165

This allows the animals to completely fill their lungs during intense locomotion, and thus remain aerobically active for a long time. Reptile_sentence_166

Tegu lizards are known to possess a proto-diaphragm, which separates the pulmonary cavity from the visceral cavity. Reptile_sentence_167

While not actually capable of movement, it does allow for greater lung inflation, by taking the weight of the viscera off the lungs. Reptile_sentence_168

Crocodilians actually have a muscular diaphragm that is analogous to the mammalian diaphragm. Reptile_sentence_169

The difference is that the muscles for the crocodilian diaphragm pull the pubis (part of the pelvis, which is movable in crocodilians) back, which brings the liver down, thus freeing space for the lungs to expand. Reptile_sentence_170

This type of diaphragmatic setup has been referred to as the "hepatic piston". Reptile_sentence_171

The airways form a number of double tubular chambers within each lung. Reptile_sentence_172

On inhalation and exhalation air moves through the airways in the same direction, thus creating a unidirectional airflow through the lungs. Reptile_sentence_173

A similar system is found in birds, monitor lizards and iguanas. Reptile_sentence_174

Most reptiles lack a secondary palate, meaning that they must hold their breath while swallowing. Reptile_sentence_175

Crocodilians have evolved a bony secondary palate that allows them to continue breathing while remaining submerged (and protect their brains against damage by struggling prey). Reptile_sentence_176

Skinks (family Scincidae) also have evolved a bony secondary palate, to varying degrees. Reptile_sentence_177

Snakes took a different approach and extended their trachea instead. Reptile_sentence_178

Their tracheal extension sticks out like a fleshy straw, and allows these animals to swallow large prey without suffering from asphyxiation. Reptile_sentence_179

Turtles and tortoises Reptile_section_17

How turtles and tortoises breathe has been the subject of much study. Reptile_sentence_180

To date, only a few species have been studied thoroughly enough to get an idea of how those turtles breathe. Reptile_sentence_181

The varied results indicate that turtles and tortoises have found a variety of solutions to this problem. Reptile_sentence_182

The difficulty is that most turtle shells are rigid and do not allow for the type of expansion and contraction that other amniotes use to ventilate their lungs. Reptile_sentence_183

Some turtles, such as the Indian flapshell (Lissemys punctata), have a sheet of muscle that envelops the lungs. Reptile_sentence_184

When it contracts, the turtle can exhale. Reptile_sentence_185

When at rest, the turtle can retract the limbs into the body cavity and force air out of the lungs. Reptile_sentence_186

When the turtle protracts its limbs, the pressure inside the lungs is reduced, and the turtle can suck air in. Reptile_sentence_187

Turtle lungs are attached to the inside of the top of the shell (carapace), with the bottom of the lungs attached (via connective tissue) to the rest of the viscera. Reptile_sentence_188

By using a series of special muscles (roughly equivalent to a diaphragm), turtles are capable of pushing their viscera up and down, resulting in effective respiration, since many of these muscles have attachment points in conjunction with their forelimbs (indeed, many of the muscles expand into the limb pockets during contraction). Reptile_sentence_189

Breathing during locomotion has been studied in three species, and they show different patterns. Reptile_sentence_190

Adult female green sea turtles do not breathe as they crutch along their nesting beaches. Reptile_sentence_191

They hold their breath during terrestrial locomotion and breathe in bouts as they rest. Reptile_sentence_192

North American box turtles breathe continuously during locomotion, and the ventilation cycle is not coordinated with the limb movements. Reptile_sentence_193

This is because they use their abdominal muscles to breathe during locomotion. Reptile_sentence_194

The last species to have been studied is the red-eared slider, which also breathes during locomotion, but takes smaller breaths during locomotion than during small pauses between locomotor bouts, indicating that there may be mechanical interference between the limb movements and the breathing apparatus. Reptile_sentence_195

Box turtles have also been observed to breathe while completely sealed up inside their shells. Reptile_sentence_196

Skin Reptile_section_18

Reptilian skin is covered in a horny epidermis, making it watertight and enabling reptiles to live on dry land, in contrast to amphibians. Reptile_sentence_197

Compared to mammalian skin, that of reptiles is rather thin and lacks the thick dermal layer that produces leather in mammals. Reptile_sentence_198

Exposed parts of reptiles are protected by scales or scutes, sometimes with a bony base (osteoderms), forming armor. Reptile_sentence_199

In lepidosaurians, such as lizards and snakes, the whole skin is covered in overlapping epidermal scales. Reptile_sentence_200

Such scales were once thought to be typical of the class Reptilia as a whole, but are now known to occur only in lepidosaurians. Reptile_sentence_201

The scales found in turtles and crocodiles are of dermal, rather than epidermal, origin and are properly termed scutes. Reptile_sentence_202

In turtles, the body is hidden inside a hard shell composed of fused scutes. Reptile_sentence_203

Lacking a thick dermis, reptilian leather is not as strong as mammalian leather. Reptile_sentence_204

It is used in leather-wares for decorative purposes for shoes, belts and handbags, particularly crocodile skin. Reptile_sentence_205

Shedding Reptile_section_19

Reptiles shed their skin through a process called ecdysis which occurs continuously throughout their lifetime. Reptile_sentence_206

In particular, younger reptiles tend to shed once every 5–6 weeks while adults shed 3–4 times a year. Reptile_sentence_207

Younger reptiles shed more because of their rapid growth rate. Reptile_sentence_208

Once full size, the frequency of shedding drastically decreases. Reptile_sentence_209

The process of ecdysis involves forming a new layer of skin under the old one. Reptile_sentence_210

Proteolytic enzymes and lymphatic fluid is secreted between the old and new layers of skin. Reptile_sentence_211

Consequently, this lifts the old skin from the new one allowing shedding to occur. Reptile_sentence_212

Snakes will shed from the head to the tail while lizards shed in a "patchy pattern". Reptile_sentence_213

Dysecdysis, a common skin disease in snakes and lizards, will occur when ecdysis, or shedding, fails. Reptile_sentence_214

There are numerous reasons why shedding fails and can be related to inadequate humidity and temperature, nutritional deficiencies, dehydration and traumatic injuries. Reptile_sentence_215

Nutritional deficiencies decrease proteolytic enzymes while dehydration reduces lymphatic fluids to separate the skin layers. Reptile_sentence_216

Traumatic injuries on the other hand, form scars that will not allow new scales to form and disrupt the process of ecdysis. Reptile_sentence_217

Excretion Reptile_section_20

Excretion is performed mainly by two small kidneys. Reptile_sentence_218

In diapsids, uric acid is the main nitrogenous waste product; turtles, like mammals, excrete mainly urea. Reptile_sentence_219

Unlike the kidneys of mammals and birds, reptile kidneys are unable to produce liquid urine more concentrated than their body fluid. Reptile_sentence_220

This is because they lack a specialized structure called a loop of Henle, which is present in the nephrons of birds and mammals. Reptile_sentence_221

Because of this, many reptiles use the colon to aid in the reabsorption of water. Reptile_sentence_222

Some are also able to take up water stored in the bladder. Reptile_sentence_223

Excess salts are also excreted by nasal and lingual salt glands in some reptiles. Reptile_sentence_224

In all reptiles the urinogenital ducts and the anus both empty into an organ called a cloaca. Reptile_sentence_225

In some reptiles, a midventral wall in the cloaca may open into a urinary bladder, but not all. Reptile_sentence_226

It is present in all turtles and tortoises as well as most lizards, but is lacking in the monitor lizard, the legless lizards. Reptile_sentence_227

It is absent in the snakes, alligators, and crocodiles. Reptile_sentence_228

Many turtles, tortoises, and lizards have proportionally very large bladders. Reptile_sentence_229

Charles Darwin noted that the Galapagos tortoise had a bladder which could store up to 20% of its body weight. Reptile_sentence_230

Such adaptations are the result of environments such as remote islands and deserts where water is very scarce. Reptile_sentence_231

Other desert-dwelling reptiles have large bladders that can store a long-term reservoir of water for up to several months and aid in osmoregulation. Reptile_sentence_232

Turtles have two or more accessory urinary bladders, located lateral to the neck of the urinary bladder and dorsal to the pubis, occupying a significant portion of their body cavity. Reptile_sentence_233

Their bladder is also usually bilobed with a left and right section. Reptile_sentence_234

The right section is located under the liver, which prevents large stones from remaining in that side while the left section is more likely to have calculi. Reptile_sentence_235

Digestion Reptile_section_21

Most reptiles are insectivorous or carnivorous and have simple and comparatively short digestive tracts due to meat being fairly simple to break down and digest. Reptile_sentence_236

Digestion is slower than in mammals, reflecting their lower resting metabolism and their inability to divide and masticate their food. Reptile_sentence_237

Their poikilotherm metabolism has very low energy requirements, allowing large reptiles like crocodiles and large constrictors to live from a single large meal for months, digesting it slowly. Reptile_sentence_238

While modern reptiles are predominantly carnivorous, during the early history of reptiles several groups produced some herbivorous megafauna: in the Paleozoic, the pareiasaurs; and in the Mesozoic several lines of dinosaurs. Reptile_sentence_239

Today, turtles are the only predominantly herbivorous reptile group, but several lines of agamas and iguanas have evolved to live wholly or partly on plants. Reptile_sentence_240

Herbivorous reptiles face the same problems of mastication as herbivorous mammals but, lacking the complex teeth of mammals, many species swallow rocks and pebbles (so called gastroliths) to aid in digestion: The rocks are washed around in the stomach, helping to grind up plant matter. Reptile_sentence_241

Fossil gastroliths have been found associated with both ornithopods and sauropods, though whether they actually functioned as a gastric mill in the latter is disputed. Reptile_sentence_242

Salt water crocodiles also use gastroliths as ballast, stabilizing them in the water or helping them to dive. Reptile_sentence_243

A dual function as both stabilizing ballast and digestion aid has been suggested for gastroliths found in plesiosaurs. Reptile_sentence_244

Nerves Reptile_section_22

The reptilian nervous system contains the same basic part of the amphibian brain, but the reptile cerebrum and cerebellum are slightly larger. Reptile_sentence_245

Most typical sense organs are well developed with certain exceptions, most notably the snake's lack of external ears (middle and inner ears are present). Reptile_sentence_246

There are twelve pairs of cranial nerves. Reptile_sentence_247

Due to their short cochlea, reptiles use electrical tuning to expand their range of audible frequencies. Reptile_sentence_248

Intelligence Reptile_section_23

See also: Animal cognition Reptile_sentence_249

Reptiles are generally considered less intelligent than mammals and birds. Reptile_sentence_250

The size of their brain relative to their body is much less than that of mammals, the encephalization quotient being about one tenth of that of mammals, though larger reptiles can show more complex brain development. Reptile_sentence_251

Larger lizards, like the monitors, are known to exhibit complex behavior, including cooperation and cognitive abilities allowing them to optimize their foraging and territoriality over time. Reptile_sentence_252

Crocodiles have relatively larger brains and show a fairly complex social structure. Reptile_sentence_253

The Komodo dragon is even known to engage in play, as are turtles, which are also considered to be social creatures, and sometimes switch between monogamy and promiscuity in their sexual behavior. Reptile_sentence_254

One study found that wood turtles were better than white rats at learning to navigate mazes. Reptile_sentence_255

Another study found that giant tortoises are capable of learning through operant conditioning, visual discrimination and retained learned behaviors with long-term memory. Reptile_sentence_256

Sea turtles have been regarded as having simple brains, but their flippers are used for a variety of foraging tasks (holding, bracing, corralling) in common with marine mammals. Reptile_sentence_257

Vision Reptile_section_24

Most reptiles are diurnal animals. Reptile_sentence_258

The vision is typically adapted to daylight conditions, with color vision and more advanced visual depth perception than in amphibians and most mammals. Reptile_sentence_259

Reptiles usually have excellent vision, allowing them to detect shapes and motions at long distances. Reptile_sentence_260

They often have only a few Rod cells and have poor vision in low-light conditions. Reptile_sentence_261

At the same time they have cells called “double cones” which give them sharp color vision and enable them to see ultraviolet wavelengths. Reptile_sentence_262

In some species, such as blind snakes, vision is reduced. Reptile_sentence_263

Many lepidosaurs have a photosensory organ on the top of their heads called the parietal eye, which are also called third eye, pineal eye or pineal gland. Reptile_sentence_264

This “eye” does not work the same way as a normal eye does as it has only a rudimentary retina and lens and thus, cannot form images. Reptile_sentence_265

It is however sensitive to changes in light and dark and can detect movement. Reptile_sentence_266

Some snakes have extra sets of visual organs (in the loosest sense of the word) in the form of pits sensitive to infrared radiation (heat). Reptile_sentence_267

Such heat-sensitive pits are particularly well developed in the pit vipers, but are also found in boas and pythons. Reptile_sentence_268

These pits allow the snakes to sense the body heat of birds and mammals, enabling pit vipers to hunt rodents in the dark. Reptile_sentence_269

Most reptiles including birds possess a nictitating membrane, a translucent third eyelid which is drawn over the eye from the inner corner. Reptile_sentence_270

Notably, it protects a crocodilian's eyeball surface while allowing a degree of vision underwater. Reptile_sentence_271

However, many squamates, geckos and snakes in particular, lack eyelids, which are replaced by a transparent scale. Reptile_sentence_272

This is called the brille, spectacle, or eyecap. Reptile_sentence_273

The brille is usually not visible, except for when the snake molts, and it protects the eyes from dust and dirt. Reptile_sentence_274

Reproduction Reptile_section_25

Reptiles generally reproduce sexually, though some are capable of asexual reproduction. Reptile_sentence_275

All reproductive activity occurs through the cloaca, the single exit/entrance at the base of the tail where waste is also eliminated. Reptile_sentence_276

Most reptiles have copulatory organs, which are usually retracted or inverted and stored inside the body. Reptile_sentence_277

In turtles and crocodilians, the male has a single median penis, while squamates, including snakes and lizards, possess a pair of hemipenes, only one of which is typically used in each session. Reptile_sentence_278

Tuatara, however, lack copulatory organs, and so the male and female simply press their cloacas together as the male discharges sperm. Reptile_sentence_279

Most reptiles lay amniotic eggs covered with leathery or calcareous shells. Reptile_sentence_280

An amnion, chorion, and allantois are present during embryonic life. Reptile_sentence_281

The eggshell (1) protects the crocodile embryo (11) and keeps it from drying out, but it is flexible to allow gas exchange. Reptile_sentence_282

The chorion (6) aids in gas exchange between the inside and outside of the egg. Reptile_sentence_283

It allows carbon dioxide to exit the egg and oxygen gas to enter the egg. Reptile_sentence_284

The albumin (9) further protects the embryo and serves as a reservoir for water and protein. Reptile_sentence_285

The allantois (8) is a sac that collects the metabolic waste produced by the embryo. Reptile_sentence_286

The amniotic sac (10) contains amniotic fluid (12) which protects and cushions the embryo. Reptile_sentence_287

The amnion (5) aids in osmoregulation and serves as a saltwater reservoir. Reptile_sentence_288

The yolk sac (2) surrounding the yolk (3) contains protein and fat rich nutrients that are absorbed by the embryo via vessels (4) that allow the embryo to grow and metabolize. Reptile_sentence_289

The air space (7) provides the embryo with oxygen while it is hatching. Reptile_sentence_290

This ensures that the embryo will not suffocate while it is hatching. Reptile_sentence_291

There are no larval stages of development. Reptile_sentence_292

Viviparity and ovoviviparity have evolved in many extinct clades of reptiles and in squamates. Reptile_sentence_293

In the latter group, many species, including all boas and most vipers, utilize this mode of reproduction. Reptile_sentence_294

The degree of viviparity varies; some species simply retain the eggs until just before hatching, others provide maternal nourishment to supplement the yolk, and yet others lack any yolk and provide all nutrients via a structure similar to the mammalian placenta. Reptile_sentence_295

The earliest documented case of viviparity in reptiles is the Early Permian mesosaurs, although some individuals or taxa in that clade may also have been oviparous because a putative isolated egg has also been found. Reptile_sentence_296

Several groups of Mesozoic marine reptiles also exhibited viviparity, such as mosasaurs, ichthyosaurs, and Sauropterygia, a group that include pachypleurosaurs and Plesiosauria. Reptile_sentence_297

Asexual reproduction has been identified in squamates in six families of lizards and one snake. Reptile_sentence_298

In some species of squamates, a population of females is able to produce a unisexual diploid clone of the mother. Reptile_sentence_299

This form of asexual reproduction, called parthenogenesis, occurs in several species of gecko, and is particularly widespread in the teiids (especially Aspidocelis) and lacertids (Lacerta). Reptile_sentence_300

In captivity, Komodo dragons (Varanidae) have reproduced by parthenogenesis. Reptile_sentence_301

Parthenogenetic species are suspected to occur among chameleons, agamids, xantusiids, and typhlopids. Reptile_sentence_302

Some reptiles exhibit temperature-dependent sex determination (TDSD), in which the incubation temperature determines whether a particular egg hatches as male or female. Reptile_sentence_303

TDSD is most common in turtles and crocodiles, but also occurs in lizards and tuatara. Reptile_sentence_304

To date, there has been no confirmation of whether TDSD occurs in snakes. Reptile_sentence_305

Defense mechanisms Reptile_section_26

Many small reptiles, such as snakes and lizards that live on the ground or in the water, are vulnerable to being preyed on by all kinds of carnivorous animals. Reptile_sentence_306

Thus avoidance is the most common form of defense in reptiles. Reptile_sentence_307

At the first sign of danger, most snakes and lizards crawl away into the undergrowth, and turtles and crocodiles will plunge into water and sink out of sight. Reptile_sentence_308

Camouflage and warning Reptile_section_27

Reptiles tend to avoid confrontation through camouflage. Reptile_sentence_309

Two major groups of reptile predators are birds and other reptiles, both of which have well developed color vision. Reptile_sentence_310

Thus the skins of many reptiles have cryptic coloration of plain or mottled gray, green, and brown to allow them to blend into the background of their natural environment. Reptile_sentence_311

Aided by the reptiles' capacity for remaining motionless for long periods, the camouflage of many snakes is so effective that people or domestic animals are most typically bitten because they accidentally step on them. Reptile_sentence_312

When camouflage fails to protect them, blue-tongued skinks will try to ward off attackers by displaying their blue tongues, and the frill-necked lizard will display its brightly colored frill. Reptile_sentence_313

These same displays are used in territorial disputes and during courtship. Reptile_sentence_314

If danger arises so suddenly that flight is useless, crocodiles, turtles, some lizards, and some snakes hiss loudly when confronted by an enemy. Reptile_sentence_315

Rattlesnakes rapidly vibrate the tip of the tail, which is composed of a series of nested, hollow beads to ward of approaching danger. Reptile_sentence_316

In contrast to the normal drab coloration of most reptiles, the lizards of the genus Heloderma (the Gila monster and the beaded lizard) and many of the coral snakes have high-contrast warning coloration, warning potential predators they are venomous. Reptile_sentence_317

A number of non-venomous North American snake species have colorful markings similar to those of the coral snake, an oft cited example of Batesian mimicry. Reptile_sentence_318

Alternative defense in snakes Reptile_section_28

Further information: Venom and Evolution of snake venom Reptile_sentence_319

Camouflage does not always fool a predator. Reptile_sentence_320

When caught out, snake species adopt different defensive tactics and use a complicated set of behaviors when attacked. Reptile_sentence_321

Some first elevate their head and spread out the skin of their neck in an effort to look large and threatening. Reptile_sentence_322

Failure of this strategy may lead to other measures practiced particularly by cobras, vipers, and closely related species, which use venom to attack. Reptile_sentence_323

The venom is modified saliva, delivered through fangs from a venom gland. Reptile_sentence_324

Some non-venomous snakes, such as American hognose snakes or European grass snake, play dead when in danger; some, including the grass snake, exude a foul-smelling liquid to deter attackers. Reptile_sentence_325

Defense in crocodilians Reptile_section_29

When a crocodilian is concerned about its safety, it will gape to expose the teeth and yellow tongue. Reptile_sentence_326

If this doesn't work, the crocodilian gets a little more agitated and typically begins to make hissing sounds. Reptile_sentence_327

After this, the crocodilian will start to change its posture dramatically to make itself look more intimidating. Reptile_sentence_328

The body is inflated to increase apparent size. Reptile_sentence_329

If absolutely necessary it may decide to attack an enemy. Reptile_sentence_330

Some species try to bite immediately. Reptile_sentence_331

Some will use their heads as sledgehammers and literally smash an opponent, some will rush or swim toward the threat from a distance, even chasing the opponent onto land or galloping after it. Reptile_sentence_332

The main weapon in all crocodiles is the bite, which can generate very high bite force. Reptile_sentence_333

Many species also possess canine-like teeth. Reptile_sentence_334

These are used primarily for seizing prey, but are also used in fighting and display. Reptile_sentence_335

Shedding and regenerating tails Reptile_section_30

Main article: Autotomy Reptile_sentence_336

Geckos, skinks, and other lizards that are captured by the tail will shed part of the tail structure through a process called autotomy and thus be able to flee. Reptile_sentence_337

The detached tail will continue to wiggle, creating a deceptive sense of continued struggle and distracting the predator's attention from the fleeing prey animal. Reptile_sentence_338

The detached tails of leopard geckos can wiggle for up to 20 minutes. Reptile_sentence_339

In many species the tails are of a separate and dramatically more intense color than the rest of the body so as to encourage potential predators to strike for the tail first. Reptile_sentence_340

In the shingleback skink and some species of geckos, the tail is short and broad and resembles the head, so that the predators may attack it rather than the more vulnerable front part. Reptile_sentence_341

Reptiles that are capable of shedding their tails can partially regenerate them over a period of weeks. Reptile_sentence_342

The new section will however contain cartilage rather than bone, and will never grow to the same length as the original tail. Reptile_sentence_343

It is often also distinctly discolored compared to the rest of the body and may lack some of the external sculpting features seen in the original tail. Reptile_sentence_344

Relations with humans Reptile_section_31

Further information: Human uses of reptiles Reptile_sentence_345

In cultures and religions Reptile_section_32

Main article: Reptiles in culture Reptile_sentence_346

Dinosaurs have been widely depicted in culture since the English palaeontologist Richard Owen coined the name dinosaur in 1842. Reptile_sentence_347

As soon as 1854, the Crystal Palace Dinosaurs were on display to the public in south London. Reptile_sentence_348

One dinosaur appeared in literature even earlier, as Charles Dickens placed a Megalosaurus in the first chapter of his novel Bleak House in 1852. Reptile_sentence_349

The dinosaurs featured in books, films, television programs, artwork, and other media have been used for both education and entertainment. Reptile_sentence_350

The depictions range from the realistic, as in the television documentaries of the 1990s and first decade of the 21st century, or the fantastic, as in the monster movies of the 1950s and 1960s. Reptile_sentence_351

The snake or serpent has played a powerful symbolic role in different cultures. Reptile_sentence_352

In Egyptian history, the Nile cobra adorned the crown of the pharaoh. Reptile_sentence_353

It was worshipped as one of the gods and was also used for sinister purposes: murder of an adversary and ritual suicide (Cleopatra). Reptile_sentence_354

In Greek mythology snakes are associated with deadly antagonists, as a chthonic symbol, roughly translated as earthbound. Reptile_sentence_355

The nine-headed Lernaean Hydra that Hercules defeated and the three Gorgon sisters are children of Gaia, the earth. Reptile_sentence_356

Medusa was one of the three Gorgon sisters who Perseus defeated. Reptile_sentence_357

Medusa is described as a hideous mortal, with snakes instead of hair and the power to turn men to stone with her gaze. Reptile_sentence_358

After killing her, Perseus gave her head to Athena who fixed it to her shield called the Aegis. Reptile_sentence_359

The Titans are depicted in art with their legs replaced by bodies of snakes for the same reason: They are children of Gaia, so they are bound to the earth. Reptile_sentence_360

In Hinduism, snakes are worshipped as gods, with many women pouring milk on snake pits. Reptile_sentence_361

The cobra is seen on the neck of Shiva, while Vishnu is depicted often as sleeping on a seven-headed snake or within the coils of a serpent. Reptile_sentence_362

There are temples in India solely for cobras sometimes called Nagraj (King of Snakes), and it is believed that snakes are symbols of fertility. Reptile_sentence_363

In the annual Hindu festival of Nag Panchami, snakes are venerated and prayed to. Reptile_sentence_364

In religious terms, the snake and jaguar are arguably the most important animals in ancient Mesoamerica. Reptile_sentence_365

"In states of ecstasy, lords dance a serpent dance; great descending snakes adorn and support buildings from Chichen Itza to Tenochtitlan, and the Nahuatl word coatl meaning serpent or twin, forms part of primary deities such as Mixcoatl, Quetzalcoatl, and Coatlicue." Reptile_sentence_366

In Christianity and Judaism, a serpent appears in Genesis to tempt Adam and Eve with the forbidden fruit from the Tree of Knowledge of Good and Evil. Reptile_sentence_367

The turtle has a prominent position as a symbol of steadfastness and tranquility in religion, mythology, and folklore from around the world. Reptile_sentence_368

A tortoise's longevity is suggested by its long lifespan and its shell, which was thought to protect it from any foe. Reptile_sentence_369

In the cosmological myths of several cultures a World Turtle carries the world upon its back or supports the heavens. Reptile_sentence_370

Medicine Reptile_section_33

See also: Epidemiology of snakebites Reptile_sentence_371

Deaths from snakebites are uncommon in many parts of the world, but are still counted in tens of thousands per year in India. Reptile_sentence_372

Snakebite can be treated with antivenom made from the venom of the snake. Reptile_sentence_373

To produce antivenom, a mixture of the venoms of different species of snake is injected into the body of a horse in ever-increasing dosages until the horse is immunized. Reptile_sentence_374

Blood is then extracted; the serum is separated, purified and freeze-dried. Reptile_sentence_375

The cytotoxic effect of snake venom is being researched as a potential treatment for cancers. Reptile_sentence_376

Lizards such as the Gila monster produce toxins with medical applications. Reptile_sentence_377

Gila toxin reduces plasma glucose; the substance is now synthesised for use in the anti-diabetes drug exenatide (Byetta). Reptile_sentence_378

Another toxin from Gila monster saliva has been studied for use as an anti-Alzheimer's drug. Reptile_sentence_379

Geckos have also been used as medicine, especially in China. Reptile_sentence_380

Turtles have been used in Chinese traditional medicine for thousands of years, with every part of the turtle believed to have medical benefits. Reptile_sentence_381

There is a lack of scientific evidence that would correlate claimed medical benefits to turtle consumption. Reptile_sentence_382

Growing demand for turtle meat has placed pressure on vulnerable wild populations of turtles. Reptile_sentence_383

Commercial farming Reptile_section_34

See also: Crocodile farm, Snake farm, and Turtle farming Reptile_sentence_384

Crocodiles are protected in many parts of the world, and are farmed commercially. Reptile_sentence_385

Their hides are tanned and used to make leather goods such as shoes and handbags; crocodile meat is also considered a delicacy. Reptile_sentence_386

The most commonly farmed species are the saltwater and Nile crocodiles. Reptile_sentence_387

Farming has resulted in an increase in the saltwater crocodile population in Australia, as eggs are usually harvested from the wild, so landowners have an incentive to conserve their habitat. Reptile_sentence_388

Crocodile leather is made into wallets, briefcases, purses, handbags, belts, hats, and shoes. Reptile_sentence_389

Crocodile oil has been used for various purposes. Reptile_sentence_390

Snakes are also farmed, primarily in East and Southeast Asia, and their production has become more intensive in the last decade. Reptile_sentence_391

Snake farming has been troubling for conservation in the past as it can lead to overexploitation of wild snakes and their natural prey to supply the farms. Reptile_sentence_392

However, farming snakes can limit the hunting of wild snakes, while reducing the slaughter of higher-order vertebrates like cows. Reptile_sentence_393

The energy efficiency of snakes is higher than expected for carnivores, due to their ectothermy and low metabolism. Reptile_sentence_394

Waste protein from the poultry and pig industries is used as feed in snake farms. Reptile_sentence_395

Snake farms produce meat, snake skin, and antivenom. Reptile_sentence_396

Turtle farming is another known but controversial practice. Reptile_sentence_397

Turtles have been farmed for a variety of reasons, ranging from food to traditional medicine, the pet trade, and scientific conservation. Reptile_sentence_398

Demand for turtle meat and medicinal products is one of the main threats to turtle conservation in Asia. Reptile_sentence_399

Though commercial breeding would seem to insulate wild populations, it can stoke the demand for them and increase wild captures. Reptile_sentence_400

Even the potentially appealing concept of raising turtles at a farm to release into the wild is questioned by some veterinarians who have had some experience with farm operations. Reptile_sentence_401

They caution that this may introduce into the wild populations infectious diseases that occur on the farm, but have not (yet) been occurring in the wild. Reptile_sentence_402

Reptiles in captivity Reptile_section_35

Further information: Herpetoculture Reptile_sentence_403

In the Western world, some snakes (especially docile species such as the ball python and corn snake) are kept as pets. Reptile_sentence_404

Numerous species of lizard are kept as pets, including bearded dragons, iguanas, anoles, and geckos (such as the popular leopard gecko). Reptile_sentence_405

Turtles and tortoises are an increasingly popular pet, but keeping them can be challenging due to particular requirements, such as temperature control and a varied diet, as well as the long lifespans of turtles, who can potentially outlive their owners. Reptile_sentence_406

Good hygiene and significant maintenance is necessary when keeping reptiles, due to the risks of Salmonella and other pathogens. Reptile_sentence_407

A herpetarium is a zoological exhibition space for reptiles or amphibians. Reptile_sentence_408

See also Reptile_section_36


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