The Procolophonia are a suborder of

herbivorous A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthpar ...

reptiles that lived from the Middle Permian till the end of the Triassic period. They were originally included as a suborder of the

Cotylosauria Fossil of '' Labidosaurus hamatus'' Captorhinida (older name: Cotylosauria) is a doubly paraphyletic grouping of early reptiles. Robert L. Carroll (1988) ranked it as an order in the subclass Anapsida, composed of the following suborders:R. L. Ca ...

(later renamed

Captorhinida Fossil of '' Labidosaurus hamatus'' Captorhinida (older name: Cotylosauria) is a doubly paraphyletic grouping of early reptiles. Robert L. Carroll (1988) ranked it as an order in the subclass Anapsida, composed of the following suborders:R. L. Ca ...

Carroll 1988) but are now considered a clade of

Parareptilia Parareptilia ("at the side of reptiles") is a subclass or clade of basal sauropsids (reptiles), typically considered the sister taxon to Eureptilia (the group that likely contains all living reptiles and birds). Parareptiles first arose near th ...

. They are closely related to other generally lizard-like Permian reptiles such as the

Millerettidae Millerettidae is an extinct family of parareptiles from the Middle Permian to the Late Permian period (Capitanian - Changhsingian stages) of South Africa. The millerettids were small insectivores and probably resembled modern lizards in appearanc ...

Bolosauridae Bolosauridae is an extinct family of ankyramorph parareptiles known from the latest Carboniferous (Gzhelian) or earliest Permian (Asselian) to the early Guadalupian epoch (latest Roadian stage) of North America, China, Germany, Russia and France. ...

, Acleistorhinidae, and Lanthanosuchidae, all of which are included under the

Anapsida An anapsid is an amniote whose skull lacks one or more skull openings (fenestra, or fossae) near the temples. Traditionally, the Anapsida are the most primitive subclass of amniotes, the ancestral stock from which Synapsida and Diapsida evolved ...

or "Parareptiles" (as opposed to the

Eureptilia Eureptilia ("true reptiles") is one of the two major subgroups of the clade Sauropsida, the other one being Parareptilia. Eureptilia includes Diapsida (the clade containing all modern reptiles and birds), as well as a number of primitive Permo ...

Classification

There are two main groups of Procolophonia, the small, lizard-like Procolophonoidea, and the

Pareiasauroidea Pareiasaurs (meaning "cheek lizards") are an extinct clade of large, herbivorous parareptiles. Members of the group were armoured with scutes which covered large areas of the body. They first appeared in southern Pangea during the Middle Permian ...

, which include the large, armoured Pareiasauridae. According to the traditional classification of Carroll 1988 as well as recent

phylogenetic analyses In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...

, smaller groups like

Rhipaeosauridae Nycteroleteridae is a family of procolophonian parareptilians (extinct early reptiles) from the Middle to Late Permian of Russia and North America. They are sometimes classified as a sister group to pareiasaurids (but see ''Classification)'' ...

(now a synonym of Nycteroleteridae) and Sclerosauridae are classified with the pareiasaurs and with the

procolophonid Procolophonidae is an extinct family of small, lizard-like parareptiles known from the Late Permian to Late Triassic that were distributed across Pangaea, having been reported from Europe, North America, China, South Africa, South America, Antarc ...

s, respectively. The Nyctiphruretidae was thought to represent the

sister taxon In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and ...

of Procolophonia by many studies, however recently discovered material places it within the group, as the sister taxon of Procolophonoidea. The following

cladogram A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to ...

is simplified after the phylogenetic analysis of MacDougall and Reisz (2014) and shows the placement of Procolophonia within

. Relationships within bolded terminal clades are not shown.

Relationship to turtles

The procolophonians were traditionally thought to be ancestral to the

turtle Turtles are an order of reptiles known as Testudines, characterized by a special shell developed mainly from their ribs. Modern turtles are divided into two major groups, the Pleurodira (side necked turtles) and Cryptodira (hidden necked t ...

s, although experts disagreed over whether turtle ancestors would be found among the Procolophonidae, the Pareiasauridae (Lee 1995,1996, 1997), or simply a generic Procolophonian ancestor. Laurin & Reisz, 1995 and Laurin &

Gauthier Gauthier () is a French name of Germanic origin, corresponding to the English given name Walter. People with the given name * Gauthier de Costes, seigneur de la Calprenède * Gauthier de Brienne, Counts Walter III of Brienne, Walter IV of Brienne, ...

1996 defined the Procolophonia cladistically as "The most recent common ancestor of pareiasaurs, procolophonids, and testudines (Chelonia), and all its descendants", and listed a number of

autapomorphies In phylogenetics, an autapomorphy is a distinctive feature, known as a derived trait, that is unique to a given taxon. That is, it is found only in one taxon, but not found in any others or outgroup taxa, not even those most closely related to t ...

. However, Rieppel and deBraga 1996 and deBraga & Rieppel, 1997 argued that turtles evolved from

Sauropterygia Sauropterygia ("lizard flippers") is an extinct taxon of diverse, aquatic reptiles that developed from terrestrial ancestors soon after the end-Permian extinction and flourished during the Triassic before all except for the Plesiosauria became ...

ns, which would mean that the Parareptilia and Procolophonia constitute wholly extinct clades that are only distantly related to living reptiles. The first genome-wide phylogenetic analysis of turtle relationships was completed by Wang et al. (2013). Using the draft genomes of ''Chelonia mydas'' and ''Pelodiscus sinensis,'' the team used the largest turtle data set to date in their analysis and concluded that turtles are likely a sister group of crocodilians and birds ( Archosauria). This placement within the diapsids suggests that the turtle lineage lost diapsid skull characteristics as it now possesses an anapsid skull.

References

;Notes ;Sources * Carroll, R. L., (1988), ''

Vertebrate Paleontology and Evolution ''Vertebrate Paleontology and Evolution'' is an advanced textbook on vertebrate paleontology by Robert L. Carroll, published in 1988 by WH Freeman. It provides a very detailed technical account of various groups of living and fossil vertebrate ...

'' (incl. Appendix; Vertebrate Classification), W.H. Freeman & Co. New York * deBraga M. & O. Rieppel. 1997. Reptile phylogeny and the interrelationships of turtles. Zoological Journal of the Linnean Society 120: 281-354. * Kuhn, O, 1969, Cotylosauria, part 6 of ''Handbuch der Palaoherpetologie'' ( Encyclopedia of Palaeoherpetology), Gustav Fischer Verlag, Stuttgart & Portland * Laurin, M., & Gauthier, J. A., 199
Phylogeny and Classification of Amniotes
at the

Tree of Life Web Project The Tree of Life Web Project is an Internet project providing information about the diversity and phylogeny of life on Earth. This collaborative peer reviewed project began in 1995, and is written by biologists from around the world. The site ...

* Laurin, M. & R. R. Reisz. 1995. A reevaluation of early amniote phylogeny.

Zoological Journal of the Linnean Society The ''Zoological Journal of the Linnean Society'' is a monthly peer-reviewed scientific journal covering zoology published by Oxford University Press on behalf of the Linnean Society. The editor-in-chief is Maarten Christenhusz (Linnean Society). ...

113: 165-223. * Lee, M. S. Y. 1995. Historical burden in systematics and the interrelationships of 'Parareptiles'. Biological Reviews of the Cambridge Philosophical Society 70: 459-547. * Lee M. S. Y. 1996. Correlated progression and the origin of turtles. Nature 379: 812-815. * Lee, M. S. Y., 1997: Pareiasaur phylogeny and the origin of turtles.

: Vol. 120, pp. 197–280 * Rieppel O. & M. deBraga. 1996. Turtles as diapsid reptiles. Nature 384: 453-455.

External links

Basal Anapsids
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Palaeos Palaeos.com is a web site on biology, paleontology, phylogeny and geology and which covers the history of Earth. The site is well respected and has been used as a reference by professional paleontologists such as Michael J. Benton, the professor of ...

{{Taxonbar, from=Q3406444 Procolophonomorphs Permian reptiles Triassic reptiles Guadalupian first appearances Late Triassic extinctions