Sauropareion anoplus (Modesto, Sues and Damiani 2001) earliest Triassic, ~3 cm skull length, was considered a procolophonoid, but it is not closely related to Procolophon. Derived from a sister to Macroleter and Nyctiphruretus, Sauropareion phylogenetically preceded Owenetta, Candelaria and after those, the basal lepidosauriform, Paliguana. Thus, Sauropareion leads us closer to the base of the Lepidosauria.
Distinct from Macroleter and Nyctiphruretus, the skull of Sauropareion emphasized the dorsal process of the quadratojugal so that it broadly contacted the jugal above the lateral temporal fenestra while simultaneously deleting the lower temporal bar. This is a big change facilitated by the earlier appearance of the dorsal process of the quadratojugal in Macroleter above its tiny lateral temporal fenestra. The posterior skull was lower, narrower and shorter as the orbit was relatively larger. The mandible included a retroarticular process.
A recent paper by MacDougall et al. (2012) presented the postcranial skeleton of Sauropareion sans the tail. Here the manus and pes are reconstructed with PILs. Six or fewer cervicals were present. The posterior dorsal vertebrae were ribless. The pelvis is difficult to reconstruct in its entirety. The astragalus and calcaneum were fused. These authors also considered Sauropareion the sister to other procolophonids, but the present tree does not. The authors considered Sauropareion a burrower based on a spade-shaped skull, robust phalanges and large unguals.
MacDougall et al. (2012) considered Nyctiphruretus and the Owenettidae basal to the Procolophonidae. Colletta was a basal procolophonid with Sauropareion as a sister. All the other so-called procolophonids, including Sclerosaurus and Hypsognathus nested in an unresolved bush.
In the present tree (segment at right) Procolophon is a sister to Diadectes, only distantly related to Nyctiphruretus, Sauropareion, Coletta and the owenettids. Adding taxa to the MacDougall et al. (2012) would have solved their problem.
Coletta was tested and it nested with Sauropareion as a sister. They may be congeneric.