Difference between revisions of "Squamata" - New World Encyclopedia

Revision as of 03:15, 1 December 2007

Scaled reptiles

Brown tree snake and Green anole

Scientific classification

Kingdom:	Animalia
Phylum:	Chordata
Class:	Sauropsida
Order:	Squamata Oppel, 1811

black: range of Squamata

Suborders

see text

Squamata (scaled reptiles) is the most diverse order of reptiles, comprised of the lizards and snakes and characterized a flexible jaw structure (movable quadrate bones).

other groups.

Members of the order are distinguished by their skins, which bear horny scales or shields. They also possess movable quadrate bones, making it possible to move the upper jaw relative to the braincase. This is particularly visible in snakes, which are able to open their mouths very widely to accommodate comparatively large prey. The male members of the group Squamata are the only vertebrates with a hemipenis. This is also the only reptile group in which can be found both viviparous and ovoviviparous species, as well as the usual oviparous reptiles.

According to a report by Uetz in 2000, comprehensive compilations reveal a total of 7,870 species of reptiles, with the majority being lizards (4,470 species) and snakes (2,920), and with 23 described species of living crocodiles, 295 species of turtles, 156 amphisbaenias, and 2 species of tuataras.

Overview

Reptiles are tetrapods (four-legged vertebrates) and amniotes (animals whose embryos are surrounded by an amniotic membrane that encases it in amniotic fluid). Reptiles have traditionally been defined as including all the amniotes except birds and mammals.

Today, reptiles are represented by four surviving orders:

Crocodilia (crocodiles, caimans, and alligators)
Rhynchocephalia (tuataras from New Zealand)
Squamata (lizards, snakes, and amphisbaenids ("worm-lizards")
Testudines (turtles)

Classification

Classical

Classically, the order is divided into three suborders:

Lacertilia, the lizards;
Serpentes, the snakes;
Amphisbaenia, the worm lizards.

Describe each briefly

Of these, the lizards form a paraphyletic group.

More recent

In newer classifications the name Sauria is used for reptiles and birds in general, and the Squamata are divided differently:

Suborder Iguania (the iguanas and chameleons)
Suborder Scleroglossa
- Infraorder Gekkota (the geckos)
- Infraorder Anguimorpha (the monitors, goannas, Komodo dragon, Gila monster, and slow-worms)
- Infraorder Scincomorpha (skinks, whiptail lizards and common European lizards)
- Infraorder Serpentes (the snakes)
- Infraorder Amphisbaenia

The exact relationships within these two suborders are not entirely certain yet, though recent research strongly suggests that several families form a venom clade which encompasses a majority (nearly 60%) of Squamate species.

The Squamata do not include the tuataras, New Zealand reptiles resembling lizards.

References
ISBN links support NWE through referral fees

Grzimek, B., D. G. Kleiman, V. Geist, and M. C. McDade. 2004. Grzimek's Animal Life Encyclopedia. Detroit: Thomson-Gale. ISBN 0787657883.

Kazlev, M. A. 2007. Squamata: Overview. Palaeos.com. Retrieved November 30, 2007.

Myers, P., R. Espinosa, C. S. Parr, T. Jones, G. S. Hammond, and T. A. Dewey. 2006. Order Squamata (amphisbaenians, lizards, and snakes). Animal Diversity Web (online). Retrieved November 30, 2007.

Uetz, P. 2000. How many reptile species? Herpetological Review 31(1):13–15.

External links

Squamata

{[credit|Squamata|172960739}}

@@ Line 18: / Line 18: @@
 }}
-:''This article is about the Squamata order of reptiles. For the Roman scale armour see: [[Lorica squamata]]''.
+'''Squamata''' (scaled reptiles) is the most diverse order of [[reptile]]s, comprised of the [[lizard]]s and [[snake]]s and characterized a flexible jaw structure (movable [[quadrate bone]]s).
+other groups.
+Members of the order are distinguished by their skins, which bear horny [[scale (zoology)|scales]] or shields. They also possess movable [[quadrate bone]]s, making it possible to move the upper jaw relative to the [[braincase]]. This is particularly visible in snakes, which are able to open their mouths very widely to accommodate comparatively large prey. The male members of the group Squamata are the only vertebrates with a [[hemipenis]]. This is also the only reptile group in which can be found both [[viviparous]] and [[Ovoviviparity|ovoviviparous]] species, as well as the usual [[oviparous]] reptiles.
+According to a report by Uetz in 2000, comprehensive compilations reveal a total of 7,870 [[species]] of reptiles, with the majority being [[lizard]]s (4,470 species) and [[snake]]s (2,920), and with 23 described species of living crocodiles, 295 species of turtles, 156 [[amphisbaenia]]s, and 2 species of tuataras.
-'''Squamata''' (scaled reptiles) is the largest recent order of [[reptile]]s, including [[lizard]]s and [[snake]]s.  Members of the order are distinguished by their skins, which bear horny [[scale (zoology)|scales]] or shields. They also possess movable [[quadrate bone]]s, making it possible to move the upper jaw relative to the [[braincase]]. This is particularly visible in snakes, which are able to open their mouths very widely to accommodate comparatively large prey. The male members of the group Squamata are the only vertebrates with a [[hemipenis]]. This is also the only reptile group in which can be found both [[viviparous]] and [[Ovoviviparity|ovoviviparous]] species, as well as the usual [[oviparous]] reptiles.
 ==Overview==
@@ Line 71: / Line 86: @@
 * Myers, P., R. Espinosa, C. S. Parr, T. Jones, G. S. Hammond, and T. A. Dewey. 2006. [http://animaldiversity.ummz.umich.edu/site/accounts/classification/Squamata.html#Squamata Order Squamata (amphisbaenians, lizards, and snakes)]. ''Animal Diversity Web'' (online). Retrieved November 30, 2007.
+* Uetz, P. 2000. How many reptile species? ''Herpetological Review'' 31(1):13–15.
 ==External links==