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There are two main groups of Procolophonia, the small, lizard-like ]ea, and the ], which include the large, armoured ]idae. According to the traditional classification of Carroll 1988 as well as recent ], smaller groups like ] (now a ] of Nycteroleteridae) and ] are classified with the ]s and with the ]s, respectively.<ref name=Nycteroleteria>{{cite journal |author=Linda A. Tsuji, Johannes Müller and Robert R. Reisz |year=2012 |title=Anatomy of ''Emeroleter levis'' and the Phylogeny of the Nycteroleter Parareptiles |url=http://www.bioone.org/doi/abs/10.1080/02724634.2012.626004?journalCode=vrpa |journal=Journal of Vertebrate Paleontology |volume=32 |issue=1 |pages=45–67 |doi=10.1080/02724634.2012.626004 }}</ref> The ] was thought to represent the ] of Procolophonia by many studies, however recently discovered material places it within the group, as the sister taxon of Procolophonoidea.<ref name=Abyssomedon>{{Cite journal|author=Mark J. MacDougall and Robert R. Reisz |year=2014 |title=The first record of a nyctiphruretid parareptile from the Early Permian of North America, with a discussion of parareptilian temporal fenestration |journal=Zoological Journal of the Linnean Society |volume=172 |issue=3 |pages=616–630 |doi=10.1111/zoj.12180 }}</ref>
There are two main groups of Procolophonia, the small, lizard-like ]ea, and the ], which include the large, armoured ]idae. According to the traditional classification of Carroll 1988 as well as recent ], smaller groups like ] (now a ] of Nycteroleteridae) and ] are classified with the ]s and with the ]s, respectively.<ref name=Nycteroleteria>{{cite journal |author=Linda A. Tsuji, Johannes Müller and Robert R. Reisz |year=2012 |title=Anatomy of ''Emeroleter levis'' and the Phylogeny of the Nycteroleter Parareptiles |journal=Journal of Vertebrate Paleontology |volume=32 |issue=1 |pages=45–67 |doi=10.1080/02724634.2012.626004 }}</ref> The ] was thought to represent the ] of Procolophonia by many studies, however recently discovered material places it within the group, as the sister taxon of Procolophonoidea.<ref name=Abyssomedon>{{Cite journal|author=Mark J. MacDougall and Robert R. Reisz |year=2014 |title=The first record of a nyctiphruretid parareptile from the Early Permian of North America, with a discussion of parareptilian temporal fenestration |journal=Zoological Journal of the Linnean Society |volume=172 |issue=3 |pages=616–630 |doi=10.1111/zoj.12180 }}</ref>
The following ] 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.<ref name=Abyssomedon/>
The following ] 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.<ref name=Abyssomedon/>
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 recent phylogenetic analyses, smaller groups like Rhipaeosauridae (now a synonym 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 is simplified after the phylogenetic analysis of MacDougall and Reisz (2014) and shows the placement of Procolophonia within Parareptilia. Relationships within bolded terminal clades are not shown.
The procolophonians were traditionally thought to be ancestral to the turtles, 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
Linda A. Tsuji, Johannes Müller and Robert R. Reisz (2012). "Anatomy of Emeroleter levis and the Phylogeny of the Nycteroleter Parareptiles". Journal of Vertebrate Paleontology. 32 (1): 45–67. doi:10.1080/02724634.2012.626004.
^ Mark J. MacDougall and Robert R. Reisz (2014). "The first record of a nyctiphruretid parareptile from the Early Permian of North America, with a discussion of parareptilian temporal fenestration". Zoological Journal of the Linnean Society. 172 (3): 616–630. doi:10.1111/zoj.12180.
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.
