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An anapsid is an amniote
Amniote

The amniotes are a group of tetrapod vertebrates that have a terrestrially adapted egg. They include the Synapsida and Sauropsida . Amniote embryos, whether laid as eggs or carried by the female, are protected and aided by several extensive membranes....
 whose skull does not have openings near the temple
Temple (anatomy)

Temple indicates the side of the head behind the eyes. The bone beneath is the temporal bone....
s.

While "anapsid reptiles" or "anapsida" are traditionally spoken of as if they were a coherent group, it has been suggested that several groups of reptiles that had anapsid skulls may be only distantly related: scientists still debate the exact relationship between the basal (original) reptiles which first appeared in the late Carboniferous
Carboniferous

The Carboniferous is a geologic period that extends from the end of the Devonian period, about 359.2 ? 2.5 annum , to the beginning of the Permian period, about 299.0 ? 0.8 Ma ...
, the various Permian
Permian

The PermianThe term "Permian" was introduced into geology in 1841 by Sir Roderick Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Edouard de Verneuil; Murchison asserted in 1841 that he named his "Permian system" after the ancient kingdom...
 reptiles which had anapsid skulls, and the Testudines (turtle
Turtle

Turtles are reptiles of the Order Testudines , most of whose body is shielded by a special bone or cartilage animal shell developed from their ribs....
s, tortoise
Tortoise

Tortoises or land turtles are land-dwelling reptiles of the family of Testudinidae, order Turtle. Like their marine cousins, the sea turtles, tortoises are shielded from predators by a shell....
s, and terrapin
Terrapin

A terrapin is a chelonian living in freshwater or brackish water. The name strictly belongs to the diamondback terrapin Malaclemys terrapin, but in British English the name is widely applied to other freshwater turtles such as red-eared sliders, Trachemys scripta elegans....
s).






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An anapsid is an amniote
Amniote

The amniotes are a group of tetrapod vertebrates that have a terrestrially adapted egg. They include the Synapsida and Sauropsida . Amniote embryos, whether laid as eggs or carried by the female, are protected and aided by several extensive membranes....
 whose skull does not have openings near the temple
Temple (anatomy)

Temple indicates the side of the head behind the eyes. The bone beneath is the temporal bone....
s.

While "anapsid reptiles" or "anapsida" are traditionally spoken of as if they were a coherent group, it has been suggested that several groups of reptiles that had anapsid skulls may be only distantly related: scientists still debate the exact relationship between the basal (original) reptiles which first appeared in the late Carboniferous
Carboniferous

The Carboniferous is a geologic period that extends from the end of the Devonian period, about 359.2 ? 2.5 annum , to the beginning of the Permian period, about 299.0 ? 0.8 Ma ...
, the various Permian
Permian

The PermianThe term "Permian" was introduced into geology in 1841 by Sir Roderick Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Edouard de Verneuil; Murchison asserted in 1841 that he named his "Permian system" after the ancient kingdom...
 reptiles which had anapsid skulls, and the Testudines (turtle
Turtle

Turtles are reptiles of the Order Testudines , most of whose body is shielded by a special bone or cartilage animal shell developed from their ribs....
s, tortoise
Tortoise

Tortoises or land turtles are land-dwelling reptiles of the family of Testudinidae, order Turtle. Like their marine cousins, the sea turtles, tortoises are shielded from predators by a shell....
s, and terrapin
Terrapin

A terrapin is a chelonian living in freshwater or brackish water. The name strictly belongs to the diamondback terrapin Malaclemys terrapin, but in British English the name is widely applied to other freshwater turtles such as red-eared sliders, Trachemys scripta elegans....
s). Many modern paleontologists believe the Testudines are descended from diapsid
Diapsid

Diapsids are a group of reptiles that developed two holes in each side of their skulls, about 300 million years ago during the late Carboniferous period....
 reptiles which lost their temporal fenestrae, although that view is not generally accepted yet (see Parareptilia
Parareptilia

Parareptilia is a subclass or clade of reptiles which are variously defined as an extinct group of primitive anapsids, or a more cladistically correct alternative to Anapsida....
 for details and references).

The only living reptiles with anapsid skulls are the Testudines. The earliest fossil testudines are from the Triassic
Triassic

The Triassic is a geologic period that extends from about 251 to 199 annum . As the first period of the Mesozoic Era, the Triassic follows the Permian and is followed by the Jurassic....
, but they were already too like modern turtles to be near the start of their lineage - in particular they already had limb joints within the rib cage. The main article about Testudines covers the debate about their ancestry.

Most of the other reptiles with anapsid skulls, including the millerettids, nyctiphrurets, and pareiasaur
Pareiasaur

The Pareiasaurs - family Pareiasauridae - are a group of medium-sized to large herbivore anapsid reptiles that flourished during the Permian period....
s, became extinct in the late Permian
Permian

The PermianThe term "Permian" was introduced into geology in 1841 by Sir Roderick Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Edouard de Verneuil; Murchison asserted in 1841 that he named his "Permian system" after the ancient kingdom...
 period by the Permian-Triassic extinction event
Permian-Triassic extinction event

The Permian?Triassic extinction event, informally known as the Great Dying, was an extinction event that occurred , forming the boundary between the Permian and Triassic geologic periods....
. But the procolophonids managed to survive into the Triassic
Triassic

The Triassic is a geologic period that extends from about 251 to 199 annum . As the first period of the Mesozoic Era, the Triassic follows the Permian and is followed by the Jurassic....
.

See also

  • Parareptilia
    Parareptilia

    Parareptilia is a subclass or clade of reptiles which are variously defined as an extinct group of primitive anapsids, or a more cladistically correct alternative to Anapsida....
  • Diapsida
  • Synapsida
  • Euryapsida
    Euryapsida

    Euryapsida is a polyphyletic group of reptiles that are distinguished by a single temporal fenestra, an opening behind the orbit , under which the post-orbital and squamosal bones articulate....


External links

  • from UCMP