Procolophonia is an extinct suborder (clade) of herbivorous

reptile Reptiles, as commonly defined, are a group of tetrapods with an ectothermic metabolism and Amniotic egg, amniotic development. Living traditional reptiles comprise four Order (biology), orders: Testudines, Crocodilia, Squamata, and Rhynchocepha ...

s that lived from the Middle Permian till the end of the Triassic period. They were originally included as a suborder of the Cotylosauria (later renamed Captorhinida Carroll 1988) but are now considered a clade of

Parareptilia Parareptilia ("near-reptiles") is an extinct group of basal sauropsids (" reptiles"), traditionally considered the sister taxon to Eureptilia (the group that likely contains all living reptiles and birds). Parareptiles first arose near the en ...

. 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 appea ...

, Bolosauridae,

Acleistorhinidae Acleistorhinidae is an extinct family of Late Carboniferous and Early Permian-aged ( Moscovian to Kungurian stage) parareptiles. It is defined as a node based clade including the last common ancestor of '' Acleistorhinus pteroticus'' and '' Co ...

, and Lanthanosuchidae, all of which are included under the Anapsida or "Parareptiles" (as opposed to the Eureptilia).

Classification

There are two main groups of Procolophonia, the small, lizard-like Procolophonoidea, and the Pareiasauroidea, which include the large, armoured Pareiasauridae. According to the traditional classification of Carroll 1988 as well as

phylogenetic analyses In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as Computational phylogenetics, phylogenetic inference. It infers the relationship among organ ...

of 2012, smaller groups like Rhipaeosauridae (now a

synonym A synonym is a word, morpheme, or phrase that means precisely or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are a ...

of Nycteroleteridae) and Sclerosauridae are classified with the pareiasaurs and with the procolophonids, respectively. The Nyctiphruretidae was thought to represent the sister taxon 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 language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...

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 reptiles of the order (biology), order Testudines, characterized by a special turtle shell, shell developed mainly from their ribs. Modern turtles are divided into two major groups, the Pleurodira (side necked turtles) and Crypt ...

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 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. However, Rieppel and deBraga 1996 and deBraga & Rieppel, 1997 argued that turtles evolved from sauropterygians, 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'' (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. & R. R. Reisz. 1995. A reevaluation of early amniote phylogeny. Zoological Journal of the 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. Zoological Journal of the Linnean Society: Vol. 120, pp. 197–280 * Rieppel O. & M. deBraga. 1996. Turtles as diapsid reptiles. Nature 384: 453-455.

External links

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