Procolophonomorpha is an order or clade of early reptiles that appeared during the Middle Permian. It constitutes a diverse assemblage that includes a number of lizard-like forms, as well as more diverse types such as the pareiasaurs. The most important subclade, Procolophonia, is traditionally thought to be ancestral to (and hence to include) turtles. Lee 1995, 1996, 1997 argues that turtles evolved from pareiasaurs, but this view is by no means held unanimously. Rieppel and deBraga 1996 and deBraga and Rieppel, 1997 argue that turtles evolved from sauropterygians.
The following cladogram is simplified after the phylogenetic analysis of MacDougall and Reisz (2014) and shows the placement of Procolophonomorpha within Parareptilia and its interrelationships. Relationships within bolded terminal clades are not shown.
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. and M. deBraga. 1996. "Turtles as diapsid reptiles". Nature 384: 453–455.
^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 Society172 (3): 616–630. doi:10.1111/zoj.12180.