Revised July 13, 2014 with a new image of Sclerosaurus.
Earlier we looked at the ancestry of hard shell turtles (starting with Proganochelys) and soft shell turtles (starting with Odontochelys). According to the large reptile tree, the closest sister taxon to turtles is the clade Pareiasauria, represented above by Anthodon (Fig. 1). Stephanospondylus is basal to pareiasaurs followed more distantly diadectids, bolosaurids and ultimately Milleretta. So pareiasaurs AND turtles are sisters to diadectids and millerettids,
Sues and Reisz (2008) considered Sclerosaurus a procolophonid, but their concept of a procolophonid was much greater (includes more taxa) than is appropriate, according to the results of the large reptile tree.
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