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"Reptilia" redirects here. For other uses, see Reptile (disambiguation).
"Sauropsida" redirects here.
Reptiles
Fossil range: Carboniferous - Recent
A Tuatara, Sphenodon punctatus
A Tuatara, Sphenodon punctatus
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Subphylum: Vertebrata
Class: Sauropsida*
Goodrich, 1916
Subclasses
Synonyms

Reptiles are air-breathing, cold-blooded vertebrates that have skin covered in scales as opposed to hair or feathers. The Carboniferous is a geologic period and system that extends from the end of the Devonian period about 359 The tuatara is a reptile endemic to New Zealand which though it resembles most lizards is actually part of a distinct lineage order Sphenodontia. Chordates ( Phylum Chordata) are a group of Animals that includes the Vertebrates together with several closely related Invertebrates Vertebrates are members of the Subphylum Vertebrata, Chordates with backbones or spinal columns The grouping sometimes includes In Phylogenetics, a group of organisms is said to be paraphyletic if the group contains its most recent common ancestor but does not contain all Edwin Stephen Goodrich (b Weston-super-Mare, 21 June 1868; d Oxford, 6 January 1946) was an English zoologist specialising A class is the Taxonomic rank in the Biological classification of organisms in Biology below phylum and above order. An anapsid is an Amniote whose skull does not have openings near the temples While "anapsid reptiles" or "anapsida" are traditionally Diapsids ("two arches" are a group of Reptiles that developed two holes ( Temporal fenestra) in each side of their Skulls about 300 Million In Scientific nomenclature, synonyms are different Scientific names used for a single Taxon. Josephus Nicolaus Laurenti ( December 4, 1735 - February 17, 1805) was an Austrian naturalist. Cold-blooded organisms (called poikilotherms - "of varying temperature" maintain their body temperatures in ways different from Mammals and Birds Vertebrates are members of the Subphylum Vertebrata, Chordates with backbones or spinal columns The grouping sometimes includes In most biological nomenclature a scale ( Greek lepid, Latin squama) is a small rigid plate that grows out of an Animal They are tetrapods (having or having descended from vertebrates with four limbs) and amniotes, whose embryos are surrounded by an amniotic membrane. Tetrapods ( Greek τετραποδη tetrapoda, Latin Quadruped, "four-footed" are Vertebrate Animals The amniotes are a group of Tetrapod Vertebrates that include the Synapsida ( Mammals and Mammal-like reptiles and Sauropsida An embryo (from Greek:, plural, lit "that which grows" from en- "in" + bryein "to swell be full" is a multicellular MembraneA biological membrane or biomembrane is an enclosing or separating Amphipathic layer that acts as a barrier within or around a cell. Modern reptiles inhabit every continent with the exception of Antarctica, and are represented by four living orders:

The majority of reptile species are oviparous (egg-laying) although certain species of squamates are capable of giving live birth. A continent is one of several large Landmasses on Earth. They are generally identified by Convention rather than any strict criteria with seven regions This article is about the taxonomic rank for the sequence of species in a taxonomic list see Taxonomic order In scientific classification used Crocodilia is an order of large Reptiles that appeared about 84 million years ago in the late Cretaceous Period ( Campanian stage A crocodile is any Species belonging to the family Crocodylidae (sometimes classified instead as the Subfamily Crocodylinae) The gharial ( Gavialis gangeticus) sometimes called the Indian gavial or gavial, is one of two surviving members of the family Alligators and caimans are Archosaurs Species of Crocodilians and form the family Alligatoridae (sometimes regarded instead for differences between alligators and crocodiles please see Crocodilia An Alligator is a Crocodilian in the Genus Sphenodontia is an order of lizard-like reptiles that includes only one living genus the Tuatara ( Sphenodon) The tuatara is a reptile endemic to New Zealand which though it resembles most lizards is actually part of a distinct lineage order Sphenodontia. New Zealand is an Island country in the south-western Pacific Ocean comprising two main landmasses (the North Island and the South Island Squamata (scaled reptiles is the largest recent order of Reptiles including Lizards and Snakes Members of the order are distinguished by Lizards are a large and widespread group of Reptiles of the order Squamata, with nearly 5000 species and ranging across all continents except A snake is an elongate Reptile of the suborder Serpentes Like all reptiles snakes are covered in scales. The Amphisbaenia are a suborder of usually legless Squamates closely related to Lizards and Snakes As many species possess a pink body coloration and Turtles, Tortoises, and Terrapins are ectothermic Reptiles most of whose Body is shielded by a special Turtles are Reptiles of the Order Testudines (all living turtles belong to the Crown group Chelonia) most of Tortoises or land Turtles are land-dwelling Reptiles of the family of Testudinidae', order Testudines. In most Birds and Reptiles an egg ( Latin ovum) is the Zygote, resulting from Fertilization of the Ovum. This is achieved, either through ovoviviparity (egg retention), or viviparity (offspring born without use of calcified eggs). Ovoviviparous Animals develop within eggs that remain within the mother's body up until they hatch or are about to hatch A viviparous Animal is an animal employing vivipary: the embryo develops inside the body of the mother as opposed to outside in an egg ( Ovipary Calcium (ˈkælsiəm is the Chemical element with the symbol Ca and Atomic number 20 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. A fetus (or foetus or fœtus) is a developing Mammal or other Viviparous Vertebrate, after the Embryonic stage and The placenta is an Ephemeral organ present in placental Vertebrates, such as Eutherial Mammals and Sharks during Gestation Extant reptiles range in size from the newly-discovered Jaragua Sphaero, at 1. The Jaragua Sphaero ( Sphaerodactylus ariasae) is a Gecko Species in the Sphaerodactylus (dwarf gecko Genus. 6 cm (0. 6 in), to the Saltwater Crocodile, at up to at least 7 m (23 feet). The saltwater or estuarine crocodile ( Crocodylus porosus) is the largest of all living Crocodilians and Reptiles It is found in suitable

Contents

Classification

History of classification

Reptiles are a paraphyletic group. The group can be made monophyletic by including the birds (Aves).
Reptiles are a paraphyletic group. In Phylogenetics, a group of organisms is said to be paraphyletic if the group contains its most recent common ancestor but does not contain all The group can be made monophyletic by including the birds (Aves). A clade is a taxonomic group comprising a single Common ancestor and all the descendants of that ancestor

From the classical standpoint, reptiles included all the amniotes except birds and mammals. The amniotes are a group of Tetrapod Vertebrates that include the Synapsida ( Mammals and Mammal-like reptiles and Sauropsida Birds ( class Aves) are bipedal endothermic ( Warm-blooded) Vertebrate animals that lay eggs. Mammals ( class Mammalia) are a class of Vertebrate Animals characterized by the presence of Sweat glands, including sweat glands Thus reptiles were defined as the set of animals that includes crocodiles, alligators, tuatara, lizards, snakes, amphisbaenians and turtles, grouped together as the class Reptilia (Latin repere, "to creep"). A crocodile is any Species belonging to the family Crocodylidae (sometimes classified instead as the Subfamily Crocodylinae) for differences between alligators and crocodiles please see Crocodilia An Alligator is a Crocodilian in the Genus The tuatara is a reptile endemic to New Zealand which though it resembles most lizards is actually part of a distinct lineage order Sphenodontia. Lizards are a large and widespread group of Reptiles of the order Squamata, with nearly 5000 species and ranging across all continents except A snake is an elongate Reptile of the suborder Serpentes Like all reptiles snakes are covered in scales. The Amphisbaenia are a suborder of usually legless Squamates closely related to Lizards and Snakes As many species possess a pink body coloration and Turtles are Reptiles of the Order Testudines (all living turtles belong to the Crown group Chelonia) most of This is still the usual definition of the term. However, in recent years, many taxonomists have begun to insist that taxa should be monophyletic, that is, groups should include all descendants of a particular form. A clade is a taxonomic group comprising a single Common ancestor and all the descendants of that ancestor The reptiles as defined above would be paraphyletic, since they exclude both birds and mammals, although these also developed from the original reptile. In Phylogenetics, a group of organisms is said to be paraphyletic if the group contains its most recent common ancestor but does not contain all Colin Tudge writes:

“ Mammals are a clade, and therefore the cladists are happy to acknowledge the traditional taxon Mammalia; and birds, too, are a clade, universally ascribed to the formal taxon Aves. Cladistics is the hierarchical classification of Species based on evolutionary ancestry Mammals ( class Mammalia) are a class of Vertebrate Animals characterized by the presence of Sweat glands, including sweat glands Birds ( class Aves) are bipedal endothermic ( Warm-blooded) Vertebrate animals that lay eggs. Mammalia and Aves are, in fact, subclades within the grand clade of the Amniota. But the traditional class reptilia is not a clade. It is just a section of the clade Amniota: the section that is left after the Mammalia and Aves have been hived off. It cannot be defined by synamorphies, as is the proper way. It is instead defined by a combination of the features it has and the features it lacks: reptiles are the amniotes that lack fur or feathers. At best, the cladists suggest, we could say that the traditional Reptila are 'non-avian, non-mammalian amniotes'. [1] ”
“ By the same token, the traditional class Amphibia becomes Amphibia*, because some ancient amphibian or other gave rise to all the amniotes; and the phylum Crustacea becomes Crustacea*, because it may have given rise to the insects and myriapods (centipedes and millipedes). If we believe, as some (but not all) zoologists do, that myriapods gave rise to insects, then they should be called Myriapoda*. . . . by this convention Reptilia without an asterisk is synonymous with Amniota, and includes birds and mammals, whereas Reptilia* means non-avian, non-mammalian amniotes. [1] ”

The terms "Sauropsida" ("Lizard Faces") and "Theropsida" ("Beast Faces") were coined in 1916 by E.S. Goodrich to distinguish between lizards, birds, and their relatives on one hand (Sauropsida) and mammals and their extinct relatives (Theropsida) on the other. Synapsids ('fused arch' also known as theropsids ('beast face' are a class of Animals that includes Mammals and everything closer to mammals than Edwin Stephen Goodrich (b Weston-super-Mare, 21 June 1868; d Oxford, 6 January 1946) was an English zoologist specialising Mammals ( class Mammalia) are a class of Vertebrate Animals characterized by the presence of Sweat glands, including sweat glands 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. According to Goodrich, both lineages evolved from an earlier stem group, the Protosauria ("First Lizards") which included some Paleozoic amphibians as well as early reptiles. The Paleozoic or Palaeozoic Era (from the Greek palaio (παλαιο "old" and zoe (ζωη "life" meaning "ancient life" Prehistoric amphibian Amphibians (class Amphibia such as Frogs Toads Salamanders Newts Gymnophiona, Sirens and [2]

In 1956 D.M.S. Watson observed that the first two groups diverged very early in reptilian history, and so he divided Goodrich's Protosauria among them. David Meredith Seares Watson FRS ( 18 June 1886 – 23 July 1973) was the Jodrell Professor of Zoology and Comparative Anatomy He also reinterpreted the Sauropsida and Theropsida to exclude birds and mammals respectively. Thus his Sauropsida included Procolophonia, Eosuchia, Millerosauria, Chelonia (turtles), Squamata (lizards and snakes), Rhynchocephalia, Crocodilia, "thecodonts" (paraphyletic basal Archosauria), non-avian dinosaurs, pterosaurs, ichthyosaurs, and sauropyterygians. The Procolophonia are an suborder of herbivorous Reptiles that lived from the Middle Permian till the end of the Triassic period Eosuchians are an extinct order of Diapsid reptiles Depending on which taxa are included the order may have ranged from the late Carboniferous to The milleretids is an Extinct group of Anapsids that lived in South Africa during the Upper Permian. Turtles are Reptiles of the Order Testudines (all living turtles belong to the Crown group Chelonia) most of Squamata (scaled reptiles is the largest recent order of Reptiles including Lizards and Snakes Members of the order are distinguished by Sphenodontia is an order of lizard-like reptiles that includes only one living genus the Tuatara ( Sphenodon) Crocodilia is an order of large Reptiles that appeared about 84 million years ago in the late Cretaceous Period ( Campanian stage Thecodont ("socket-toothed" reptile now considered an obsolete term was formerly used to describe a diverse range of early Archosaurs that first appeared in the In Phylogenetics, a group of organisms is said to be paraphyletic if the group contains its most recent common ancestor but does not contain all In Phylogenetics, a basal Clade is the earliest clade to branch in a larger clade it appears at the base of a cladogram Archosaurs ( Greek for 'ruling lizards' are a group of Diapsid Reptiles represented by Modern birds and Crocodilians This group also For other meanings see Pterodactyl (disambiguation. Pterosaurs (ˈtɛrəsɔr from the Greek πτερόσαυρος pterosauros Ichthyosaurs ( Greek for 'fish lizard' - ιχθυς / ichthyos meaning 'fish' and σαυρος / sauros meaning 'lizard' were giant Sauropterygia (" Lizard Flippers quot is a group of very successful aquatic Reptiles that flourished during the Age of the Dinosaurs before [3]

This classification supplemented, but was never as popular as, the classification of the reptiles (according to Romer's classic Vertebrate Paleontology[4]) into four subclasses according to the positioning of temporal fenestrae, openings in the sides of the skull behind the eyes. Alfred Sherwood Romer ( December 28, 1894 - November 5, 1973) was an American Paleontologist and comparative Anatomist and Vertebrate Paleontology is an advanced textbook on Vertebrate paleontology by Alfred Sherwood Romer, published by the University of Chicago Press Those divisions were:

All of the above but Synapsida fall under Sauropsida. An anapsid is an Amniote whose skull does not have openings near the temples While "anapsid reptiles" or "anapsida" are traditionally Synapsids ('fused arch' also known as theropsids ('beast face' are a class of Animals that includes Mammals and everything closer to mammals than Euryapsida is a Polyphyletic (unnatural as the various members are not closely related group of Reptiles that are distinguished by a single temporal fenestra Diapsids ("two arches" are a group of Reptiles that developed two holes ( Temporal fenestra) in each side of their Skulls about 300 Million

Taxonomy

Classification to order level, after Benton, 2004. [5]

Phylogeny

The cladogram presented here illustrates the "family tree" of reptiles, and follows a simplified version of the relationships found by Laurin and Gauthier (1996), presented as part of the Tree of Life Web Project. The amniotes are a group of Tetrapod Vertebrates that include the Synapsida ( Mammals and Mammal-like reptiles and Sauropsida Synapsids ('fused arch' also known as theropsids ('beast face' are a class of Animals that includes Mammals and everything closer to mammals than The pelycosaurs (from Greek πηλυξ pelyx meaning 'bowl' and σαυρος sauros meaning 'lizard' were primitive Late Paleozoic In Phylogenetics, a group of organisms is said to be paraphyletic if the group contains its most recent common ancestor but does not contain all Therapsids are an order of Synapsids (Class Synapsida Traditionally synapsids were referred to as Reptiles and were known as Mammals ( class Mammalia) are a class of Vertebrate Animals characterized by the presence of Sweat glands, including sweat glands Reptiles, or members of the class Reptilia are air-breathing Cold-blooded Vertebrates that have skin covered in scales as opposed to hair or feathers An anapsid is an Amniote whose skull does not have openings near the temples While "anapsid reptiles" or "anapsida" are traditionally Turtles, Tortoises, and Terrapins are ectothermic Reptiles most of whose Body is shielded by a special Diapsids ("two arches" are a group of Reptiles that developed two holes ( Temporal fenestra) in each side of their Skulls about 300 Million Araeoscelidia or Araeoscelida is a Clade of extinct Diapsid Reptiles superficially resembling Lizards. Younginiformes is a replacement name for the taxon Eosuchia, proposed by Alfred Romer in 1947 Ichthyosaurs ( Greek for 'fish lizard' - ιχθυς / ichthyos meaning 'fish' and σαυρος / sauros meaning 'lizard' were giant Lepidosauromorpha is a group of Reptiles comprising all Diapsids closer to Lizards than to Archosaurs (including Crocodiles and Sauropterygia (" Lizard Flippers quot is a group of very successful aquatic Reptiles that flourished during the Age of the Dinosaurs before Placodonts (" Tablet Teeth " were a group of marine Reptiles that lived during the Triassic period becoming extinct at the end Nothosaurs (order Nothosauroidea) were Triassic marine Sauropterygian Reptiles that may have lived like seals of today catching Plesiosauria (ˌpliːsiəˈsɔriə ( Greek: plesios meaning 'near to' and sauros meaning 'lizard' are an order of Mesozoic Marine The Lepidosauria are Reptiles with overlapping scales They include the Tuataras Lizards Snakes and Amphisbaenians Lepidosaurians Sphenodontia is an order of lizard-like reptiles that includes only one living genus the Tuatara ( Sphenodon) Squamata (scaled reptiles is the largest recent order of Reptiles including Lizards and Snakes Members of the order are distinguished by Archosauromorpha ( Greek for "ruling lizard forms" is an Infraclass of Diapsid Reptiles that first appeared during the late Permian Prolacertiformes (sometimes called protorosaurs) were an order of archosauromorph Reptiles that lived during the Permian and Triassic Archosaurs ( Greek for 'ruling lizards' are a group of Diapsid Reptiles represented by Modern birds and Crocodilians This group also The Crurotarsi ("cross-ankles" are a group of archosaurs, whose name was erected as a node-based clade by Paul Sereno in 1991 The Crocodylomorpha are an important group of Archosaurs that include the Crocodilians and their extinct relatives Crocodilia is an order of large Reptiles that appeared about 84 million years ago in the late Cretaceous Period ( Campanian stage Avemetatarsalia (meaning "bird Metatarsals " is a Clade name established by British palaeontologist Michael Benton in 1999 for all Avesuchians Ornithodira is a Clade within the larger group Archosauria In 1986 Jacques Gauthier coined the name for a node clade containing the last common For other meanings see Pterodactyl (disambiguation. Pterosaurs (ˈtɛrəsɔr from the Greek πτερόσαυρος pterosauros Saurischia (sɔːˈrɪskiə, from the Greek sauros ( σαυρος) meaning 'lizard' and ischion ( ισχιον) meaning 'hip joint' Birds ( class Aves) are bipedal endothermic ( Warm-blooded) Vertebrate animals that lay eggs. Ornithischia (ɔrnɪˈθɪskiə) or Predentata is an extinct order of beaked herbivorous Dinosaurs The name ornithischia Cladistics is the hierarchical classification of Species based on evolutionary ancestry The Tree of Life Web Project is an ongoing Internet project providing information about the diversity and Phylogeny of Life on Earth [6]

Amniota

Synapsida

Reptilia
unnamed
Anapsida

Mesosauridae

unnamed

Millerettidae

unnamed

Lanthanosuchidae

unnamed

Nyctiphruretia

unnamed

Pareiasauria


Procolophonoidea



?Testudines (turtles, tortoises and terrapins)





Romeriida

Captorhinidae

unnamed

Protorothyrididae*

Diapsida

Araeoscelidia

unnamed

Younginiformes

Sauria

?Ichthyosauria


?Sauropterygia


Lepidosauromorpha (lizards, snakes, tuatara, and their extinct relatives)


Archosauromorpha (crocodiles, birds, and their extinct relatives)










Evolution

The early reptile Hylonomus
The early reptile Hylonomus

Hylonomus is the oldest-known reptile, and was about 8 to 12 inches (20 to 30 cm) long. Synapsids ('fused arch' also known as theropsids ('beast face' are a class of Animals that includes Mammals and everything closer to mammals than An anapsid is an Amniote whose skull does not have openings near the temples While "anapsid reptiles" or "anapsida" are traditionally Mesosaur ("middle lizards" were an order of small Marine reptiles that lived during the early Permian period roughly 320 to 280 million years The milleretids is an Extinct group of Anapsids that lived in South Africa during the Upper Permian. The Pareiasaurs - family Pareiasauridae - are a group of medium-sized to large herbivorous Anapsid Reptiles that flourished during the Turtles, Tortoises, and Terrapins are ectothermic Reptiles most of whose Body is shielded by a special Captorhinidae (also known as cotylosaurs or 'stem reptiles' were the earliest and most primitive reptiles Protorothyrididae was a Clade of small lizard-like reptiles possibly the ancestors of Turtles and Tortoises. In Phylogenetics, a group of organisms is said to be paraphyletic if the group contains its most recent common ancestor but does not contain all Diapsids ("two arches" are a group of Reptiles that developed two holes ( Temporal fenestra) in each side of their Skulls about 300 Million Araeoscelidia or Araeoscelida is a Clade of extinct Diapsid Reptiles superficially resembling Lizards. Younginiformes is a replacement name for the taxon Eosuchia, proposed by Alfred Romer in 1947 Sauria is a Clade of reptiles that includes all living Diapsids as well as their Common ancestor and all its extinct descendants Ichthyosaurs ( Greek for 'fish lizard' - ιχθυς / ichthyos meaning 'fish' and σαυρος / sauros meaning 'lizard' were giant Sauropterygia (" Lizard Flippers quot is a group of very successful aquatic Reptiles that flourished during the Age of the Dinosaurs before Lepidosauromorpha is a group of Reptiles comprising all Diapsids closer to Lizards than to Archosaurs (including Crocodiles and Archosauromorpha ( Greek for "ruling lizard forms" is an Infraclass of Diapsid Reptiles that first appeared during the late Permian Hylonomus ( hylo- "forest" + nomos "wanderer" was an early Reptile. Hylonomus ( hylo- "forest" + nomos "wanderer" was an early Reptile. Westlothiana has been suggested as the oldest reptile, but is for the moment considered to be more related to amphibians than amniotes. Westlothiana lizziae was a Reptile -like Tetrapod that bore a superficial resemblance to modern-day Lizards It lived during the Carboniferous The amniotes are a group of Tetrapod Vertebrates that include the Synapsida ( Mammals and Mammal-like reptiles and Sauropsida Petrolacosaurus and Mesosaurus are other examples. Petrolacosaurus was a small 40 centimeter long Diapsid reptile one of the earliest known Mesosaurus is an extinct genus of Anapsid Reptile from the early Permian period The earliest reptiles were found in the swamp forests of the Carboniferous, but were largely overshadowed by bigger labyrinthodont amphibians such as Proterogynrius. The Carboniferous is a geologic period and system that extends from the end of the Devonian period about 359 Labyrinthodont ( Greek, "maze-toothed" is an obsolete term for any member of an extinct superorder or subclass (Labyrinthodontia of Amphibians It was only after the small ice age at the end of the Carboniferous that the reptiles grew to big sizes, producing species such as Edaphosaurus and Dimetrodon. Edaphosaurus (Greek earth lizard; from edaphos / εδαφος, "ground" and sauros / σαυρος, "lizard" Dimetrodon (daɪˈmɛtɹəʊˌdɒn meaning "two measures of teeth" was a Predatory Synapsid (' Mammal-like reptile ' Genus

The first true "reptiles" (Sauropsids) are categorized as Anapsids, having a solid skull with holes only for nose, eyes, spinal cord, etc. An anapsid is an Amniote whose skull does not have openings near the temples While "anapsid reptiles" or "anapsida" are traditionally Turtles are believed by some to be surviving Anapsids, as they also share this skull structure; but this point has become contentious lately, with some arguing that turtles reverted to this primitive state in order to improve their armor. Both sides have strong evidence, and the conflict has yet to be resolved.

Shortly after the first reptiles, two branches split off, one leading to the Anapsids, which did not develop holes in their skulls. The other group, Diapsida, possessed a pair of holes in their skulls behind the eyes, along with a second pair located higher on the skull. Diapsids ("two arches" are a group of Reptiles that developed two holes ( Temporal fenestra) in each side of their Skulls about 300 Million The Diapsida split yet again into two lineages, the lepidosaurs (which contain modern snakes, lizards and tuataras, as well as, debatably, the extinct sea reptiles of the Mesozoic) and the archosaurs (today represented by only crocodilians and birds under dinosaurs, but also containing pterosaurs and non-avian dinosaurs). The Lepidosauria are Reptiles with overlapping scales They include the Tuataras Lizards Snakes and Amphisbaenians Lepidosaurians Archosaurs ( Greek for 'ruling lizards' are a group of Diapsid Reptiles represented by Modern birds and Crocodilians This group also Crocodilia is an order of large Reptiles that appeared about 84 million years ago in the late Cretaceous Period ( Campanian stage Birds ( class Aves) are bipedal endothermic ( Warm-blooded) Vertebrate animals that lay eggs. For other meanings see Pterodactyl (disambiguation. Pterosaurs (ˈtɛrəsɔr from the Greek πτερόσαυρος pterosauros

The earliest, solid-skulled amniotes also gave rise to a separate line, the Synapsida. The amniotes are a group of Tetrapod Vertebrates that include the Synapsida ( Mammals and Mammal-like reptiles and Sauropsida Synapsids ('fused arch' also known as theropsids ('beast face' are a class of Animals that includes Mammals and everything closer to mammals than Synapsids developed a pair of holes in their skulls behind the eyes (similar to the diapsids), which were used to both lighten the skull and increase the space for jaw muscles. Synapsids ('fused arch' also known as theropsids ('beast face' are a class of Animals that includes Mammals and everything closer to mammals than The synapsids eventually evolved into mammals, and are often referred to as mammal-like reptiles, though they are not true members of Sauropsida. Mammals ( class Mammalia) are a class of Vertebrate Animals characterized by the presence of Sweat glands, including sweat glands (A preferable term is "stem-mammals". )

Systems

Circulatory

Thermographic image of a monitor lizard.
Thermographic image of a monitor lizard. Monitor lizards are the family Varanidae, a group of carnivorous lizards which includes the largest living lizard the Komodo dragon.

Most reptiles have closed circulation via a three-chamber heart consisting of two atria and one, variably-partitioned ventricle. The heart is a muscular organ in all Vertebrates responsible for pumping Blood through the Blood vessels by repeated rhythmic In Anatomy, the atrium (plural atria) refers to a chamber or space In the Heart, a ventricle is a heart chamber which collects Blood from an atrium (another heart chamber that is smaller than a ventricle and There is usually one pair of aortic arches. In spite of this, because of the fluid dynamics of blood flow through the heart, there is little mixing of oxygenated and deoxygenated blood in the three-chamber heart. Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the Furthermore, the blood flow can be altered to shunt either deoxygenated blood to the body or oxygenated blood to the lungs, which gives the animal greater control over its blood flow, allowing more effective thermoregulation and longer diving times for aquatic species. There are some interesting exceptions among reptiles. For instance, crocodilians have an anatomically four-chambered heart that is capable of becoming a functionally three-chamber heart during dives (Mazzotti, 1989 pg 47). Crocodilia is an order of large Reptiles that appeared about 84 million years ago in the late Cretaceous Period ( Campanian stage Also, it has been discovered that some snake and lizard species (e. g. , monitor lizards and pythons) have three-chamber hearts that become functional four-chamber hearts during contraction. This is made possible by a muscular ridge that subdivides the ventricle during ventricular diastole and completely divides it during ventricular systole. Cardiac cycle is the term referring to all or any of the events related to the flow of blood that occur from the beginning of one heartbeat to the beginning of the next 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 (Wang et al, 2003). Squamata (scaled reptiles is the largest recent order of Reptiles including Lizards and Snakes Members of the order are distinguished by

Respiratory

All reptiles breathe using lungs. Aquatic turtles have developed more permeable skin, and some species have modified their cloaca to increase the area for gas exchange (Orenstein, 2001). Turtles are Reptiles of the Order Testudines (all living turtles belong to the Crown group Chelonia) most of Even with these adaptations, breathing is never fully accomplished without lungs. lung is the essential Respiration organ in air-breathing Animals including most Tetrapods a few Fish and a few Snails The most primitive Lung ventilation is accomplished differently in each main reptile group. In squamates the lungs are ventilated almost exclusively by the axial musculature. Squamata (scaled reptiles is the largest recent order of Reptiles including Lizards and Snakes Members of the order are distinguished by This is also the same musculature that is used during locomotion. Because of this constraint, most squamates are forced to hold their breath during intense runs. Some, however, have found a way around it. Varanids, and a few other lizard species, employ buccal pumping as a complement to their normal "axial breathing. Buccal pumping is a method of respiration using the throat muscles " This allows the animals to completely fill their lungs during intense locomotion, and thus remain aerobically active for a long time. Tegu lizards are known to possess a proto-diaphragm, which separates the pulmonary cavity from the visceral cavity. For other types of diaphragm see Diaphragm. In the Anatomy of Mammals the thoracic diaphragm is a sheet of Muscle While not actually capable of movement, it does allow for greater lung inflation, by taking the weight of the viscera off the lungs (Klein et al, 2003). Crocodilians actually have a muscular diaphragm that is analogous to the mammalian diaphragm. Crocodilia is an order of large Reptiles that appeared about 84 million years ago in the late Cretaceous Period ( Campanian stage 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. This type of diaphragmatic setup has been referred to as the "hepatic piston. "

How turtles and tortoises breathe has been the subject of much study. Turtles are Reptiles of the Order Testudines (all living turtles belong to the Crown group Chelonia) most of To date, only a few species have been studied thoroughly enough to get an idea of how turtles do it. The results indicate that turtles & tortoises have found a variety of solutions to this problem. The problem 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. Some turtles such as the Indian flapshell (Lissemys punctata) have a sheet of muscle that envelopes the lungs. When it contracts, the turtle can exhale. When at rest, the turtle can retract the limbs into the body cavity and force air out of the lungs. When the turtle protracts its limbs, the pressure inside the lungs is reduced, and the turtle can suck air in. 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. 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). For other types of diaphragm see Diaphragm. In the Anatomy of Mammals the thoracic diaphragm is a sheet of Muscle Breathing during locomotion has been studied in three species, and they show different patterns. Adult female green sea turtles do not breathe as they crutch along their nesting beaches. They hold their breath during terrestrial locomotion and breathe in bouts as they rest. North American box turtles breathe continuously during locomotion, and the ventilation cycle is not coordinated with the limb movements (Landberg et al. , 2003). They are probably using their abdominal muscles to breathe during locomotion. The last species to have been studied is red-eared sliders, which also breathe during locomotion, but they had 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. Box turtles have also been observed to breathe while completely sealed up inside their shells (ibid).

Most reptiles lack a secondary palate, meaning that they must hold their breath while swallowing. The secondary palate is an anatomical structure that divides the Nasal cavity from the oral cavity in many Vertebrates In human Embryology Crocodilians have evolved a bony secondary palate that allows them to continue breathing while remaining submerged (and protect their brains from getting kicked in by struggling prey). Skinks (family Scincidae) also have evolved a bony secondary palate, to varying degrees. Snakes took a different approach and extended their trachea instead. Their tracheal extension sticks out like a fleshy straw, and allows these animals to swallow large prey without suffering from asphyxiation.

Excretory

Excretion is performed mainly by two small kidneys. Excretion is the process of eliminating waste products of Metabolism and other non-useful materials The kidneys are complicated organs that have numerous biological roles In diapsids uric acid is the main nitrogenous waste product; turtles, like mammals, mainly excrete urea. Uric acid (or urate) is an Organic compound of Carbon, Nitrogen, Oxygen and Hydrogen with the formula C5H4N4O3 Nitrogen (ˈnaɪtɹəʤɪn is a Chemical element that has the symbol N and Atomic number 7 and Atomic weight 14 Mammals ( class Mammalia) are a class of Vertebrate Animals characterized by the presence of Sweat glands, including sweat glands Urea is an Organic compound with the Chemical formula ( N[[hydrogen H]]22 C[[oxygen O]] Unlike the kidneys of mammals and birds, reptile kidneys are unable to produce liquid urine more concentrated than their body fluid. This is because they lack a specialized structure present in the nephrons of birds and mammals, called a Loop of Henle. A nephron (from Greek νεφρός (nephros meaning "kidney" is the basic structural and functional unit of the Kidney. In the Kidney, the loop of Henle is the portion of the Nephron that leads from the Proximal convoluted tubule to the Distal convoluted tubule Because of this, many reptiles use the colon to aid in the reabsorption of water. The colon is a storage tube for solid wastes The main function of the colon appears to be extraction of Water and salts from Feces. In Physiology, reabsorption or tubular reabsorption is the flow of Glomerular filtrate from the Proximal tubule of the Nephron Some are also able to take up water stored in the bladder. In Anatomy, the urinary bladder is a hollow muscular, and distensible (or elastic organ that sits on the Pelvic floor in Mammals It is the Excess salts are also excreted by nasal and lingual salt-glands in some reptiles.

Nervous

The reptilian nervous system contains the same basic part of the amphibian brain, but the reptile cerebrum and cerebellum are slightly larger. Prehistoric amphibian Amphibians (class Amphibia such as Frogs Toads Salamanders Newts Gymnophiona, Sirens and The telencephalon (tɛlɛnˈsɛfəlɒn cerebrum, or forebrain is the most Anterior or especially in humans most Dorsal region of the The cerebellum ( Latin: "little brain" is a region of the Brain that plays an important role in the integration of sensory perception Most typical sense organs are well developed with certain exceptions most notably the snakes lack of external ears (middle and inner ears are present). All reptilians have advanced visual depth perception compared to other animals. There are twelve pairs of cranial nerves. Cranial nerves are Nerves that emerge directly from the Brain stem in contrast to Spinal nerves which emerge from segments of the Spinal cord. [1]

Reproductive

Most reptiles reproduce sexually, though some are capable of asexual reproduction. All reproductive activity occurs with the cloaca, the single exit/entrance at the base of the tail where waste is also eliminated. In zoological anatomy a cloaca is the posterior opening that serves as the only such opening for the intestinal and urinary tracts of certain animal species Tuataras lack copulatory organs, so the male and female simply press their cloacas together as the male excretes sperm. [7] Most reptiles, however, have copulatory organs, which are usually retracted or inverted and stored inside the body. In turtles and crocodilians, the male has a single median penis, while squamates including snakes and lizards possess a pair of hemipenes. The penis (plural penises, penes A hemipenis (plural hemipenes) is one of a pair of Intromittent organs of male squamates ( Snakes Lizards and worm lizards.

Most reptiles lay amniotic eggs covered with leathery or calcareous shells. An amnion, chorion and allantois are present during embryonic life. The amniotic sac is the sac in which the Fetus develops Some sources consider it to be equivalent to the Amnion. Allantois (plural allantoides or allantoises) is a part of a developing animal Conceptus (which consists of all Embryonic and extra-embryonic An embryo (from Greek:, plural, lit "that which grows" from en- "in" + bryein "to swell be full" is a multicellular There are no larval stages of development. A larva ( Latin; plural larvae) is a juvenile form of Animal with indirect development, undergoing Metamorphosis (for example Viviparity and ovoviviparity have only evolved in Squamates, and a substantial fraction of the species utilize this mode of reprduction, including all boas and most vipers. A viviparous Animal is an animal employing vivipary: the embryo develops inside the body of the mother as opposed to outside in an egg ( Ovipary Ovoviviparous Animals develop within eggs that remain within the mother's body up until they hatch or are about to hatch The degree of viviparity varies: some species simply retain the eggs until just before hatching, others provide maternal nourishment to supplement the yolk, while still others lack any yolk and provide all nutrients via a placenta. A viviparous Animal is an animal employing vivipary: the embryo develops inside the body of the mother as opposed to outside in an egg ( Ovipary

Asexual reproduction has been identified in squamates in six families of lizards and one snake. Squamata (scaled reptiles is the largest recent order of Reptiles including Lizards and Snakes Members of the order are distinguished by In some species of squamates, a population of females are able to produce a unisexual diploid clone of the mother. This asexual reproduction called parthenogenesis occurs in several species of gecko, and is particularly widespread in the teiids (especially Aspidocelis) and lacertids (Lacerta). Parthenogenesis (from the Greek παρθένος parthenos, "virgin" + γένεσις genesis, "creation" is an asexual form Geckos are small to average sized Lizards belonging to the family Gekkonidae which are found in warm climates throughout the world Teiidae is a family of Lizards native to the New World generally known as whiptails. Lacertidae is the family of the wall lizards, or true lizards, which are native to Europe, Africa, and Asia. For the biological genus of lizards see Lacerta (genus. Lacerta (ləˈsɝtə Lizard) is one of the 88 official Constellations In captivity Komodo dragons (varanidae) have reproduced by parthenogenesis. The Komodo dragon ( Varanus komodoensis) is a species of Lizard that inhabits the islands of Komodo, Rinca, Flores, Gili

Parthenogenetic species are also suspected to occur among chameleons, agamids, xantusiids, and typhlopids . Chameleons (family Chamaeleonidae) are squamates that belong to one of the best-known Lizard families Agamids, lizards of the family Agamidae, include more than 300 species in Africa, Asia, Australia, and a few in Southern Night lizards ( family name Xantusiidae are a group of very small viviparous (live-bearing Lizards, averaging from less than 4 cm to over 12 cm long Common names typical blind snakes The Typhlopidae are a family of blind Snakes They are found mostly in the tropical

References

  1. ^ a b Colin Tudge (2000). Colin Tudge (born 22 April 1943) is a British science writer A biologist by training he is the author of numerous works on food agriculture genetics 2000 ( MM) was a Leap year that started on Saturday of the Common Era, in accordance with the Gregorian calendar. The Variety of Life. Oxford University Press. ISBN 0198604262.  
  2. ^ Goodrich, E. S. (1916). "On the classification of the Reptilia". Proceedings of the Royal Society of London 89B: 261–276.  
  3. ^ Watson, D. M. S. (1957). "On Millerosaurus and the early history of the sauropsid reptiles". Philosophical Transactions of the Royal Society of London, Series B, Biological Sciences 240 (673): 325–400.  
  4. ^ Romer, A. S. (1933). Vertebrate Paleontology. University of Chicago Press.  , 3rd ed. , 1966.
  5. ^ Benton, Michael J. (2004). This page is about the paleontologist Michael J Benton For the American Foreign Service Officer see Michael L Vertebrate Paleontology, 3rd ed. , Oxford: Blackwell Science Ltd. . ISBN 0632056371.  
  6. ^ Laurin, M. and Gauthier, J. A. (1996). "Amniota. Mammals, reptiles (turtles, lizards, Sphenodon, crocodiles, birds) and their extinct relatives. " Version 01 January 1996. http://tolweb.org/Amniota/14990/1996.01.01 in The Tree of Life Web Project, http://tolweb.org/
  7. ^ Lutz, Dick (2005), Tuatara: A Living Fossil, Salem, Oregon: DIMI PRESS, ISBN 0-931625-43-2

See also

External links

This is a list of extant reptiles by family, spanning three subclasses. The following are the regional reptiles lists by continent Continent Asia Indian subcontinent Korean peninsula The amniotes are a group of Tetrapod Vertebrates that include the Synapsida ( Mammals and Mammal-like reptiles and Sauropsida An anapsid is an Amniote whose skull does not have openings near the temples While "anapsid reptiles" or "anapsida" are traditionally Synapsids ('fused arch' also known as theropsids ('beast face' are a class of Animals that includes Mammals and everything closer to mammals than Diapsids ("two arches" are a group of Reptiles that developed two holes ( Temporal fenestra) in each side of their Skulls about 300 Million

Dictionary

reptile

-noun

  1. A cold-blooded vertebrate of the Class Reptilia.
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