Pyozia – close to Orovenator

Wikipedia reports, “Pyozia (Fig. 1) is an extinct genus of basal Middle Permian varanopid synapsid known from Russia. It was first named by Jason S. Anderson and Robert R. Reisz in 2004 and the type species is Pyozia mesenensisPyozia mesenensis is known from the holotype PIN 3717/33, a three-dimensionally preserved partial skeleton including a nearly complete skull. It was collected from the Krasnoschelsk Formation, dating to the Capitanian stage of the Guadalupian epoch, about 265.8-263 million years ago.”

Pyozia in situ. Not much is known, but enough to nest it with Orovenator in the protodiapsida.

Pyozia in situ. Not much is known, but enough to nest it with Orovenator in the protodiapsida.

Anderson and Reisz (2004) nested Pyozia between Archaeovenator and Mycterosaurinae + Vanranodontidae.

In the large reptile tree (not yet updated) Pyozia nests with Orovenator (Fig 2) in the protodiapsida, which includes Archaeovenator and Mycterosaurus, outside of the Synapsida, which includes Varanops and Varanodon.

Figure 1. Orovenator (holotype on right) along with the larger referred specimen (on left, and scaled down to the size of the holotype above right). Arrows point to mismatches.

Figure 2. Orovenator (holotype on right) along with the larger referred specimen (on left, and scaled down to the size of the holotype above right). Arrows point to mismatches.

Reisz et al. 2011 nested Orovenator with Lanthanolania (a rib glider known from a skull only) and basal diapsids like Araeoscelis and basal Younginiformes like Tangasaurus, but Reisz et al. included the referred specimen, which has upper temporal fenestra. The holotype and referred specimens show several differences among the bones they share in common, so probably they are not related. Their combination creates a chimaera with traits not present in the holotype. Better to test just the holotype.

References
Anderson JS and Reisz RR 2004. Pyozia mesenensis, a new, small varanopid (Synapsida, Eupelycosauria) from Russia: “pelycosaur” diversity in the Middle Permian”. Journal of Vertebrate Paleontology 24: 173–179.
Reisz RR, Modesto SP and Scot DMT 2011. A new Early Permian reptile and its significance in early diapsid evolution. Proceedings of the Royal Society, London B

doi:10.1098/rspb.2011.0439

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