Bunostegos really is a different sort of pareiasaur
Figure 1. The skull of Bunostegos with color added for clarity. Images from Tsuji et al. 2013.
Bunostegos akokanensis (Sidor et al. 2003, Tsuji et al. 2013; Late Permian, 1.5m; MNN-MOR47, Fig. 1) is a large pareiasaur nesting close to small Elginia (Newton 1893) in the large reptile tree (640 taxa), closer to turtles than most other pareiasaurs. Analysis of the limb bones suggested a more upright stance than is typical for pareiasaurs and turtles. It lived in a desert environment. The specimen is known from parts of several specimens.
Figure 2. Elginia and Meiolania, a pre-turtle and a basal turtle, both with supratemporal and other horns, as in the outgroup pareiasaur, Bunostegos.
References
Newton ET 1893. On some new reptiles from the Elgin Sandstone: Philosophical Transactions of the Royal Society of London, series B 184:473-489.
Sidor CA, Blackburn DC and Gado B 2003. The vertebrate fauna of the Upper Permian of Niger — II, Preliminary description of a new pareiasaur. Palaeontologica Africana 39: 45–52.
Tsuji LA, Sidor CA, Steyer JSB, Smith RMH, Tabor NJ and Ide O 2013. The vertebrate fauna of the Upper Permian of Niger—VII. Cranial anatomy and relationships of Bunostegos akokanensis (Pareiasauria). Journal of Vertebrate Paleontology 33 (4): 747. doi:10.1080/02724634.2013.739537
Source: https://pterosaurheresies.wordpress.com/2016/01/30/bunostegos-really-is-a-different-sort-of-pareiasaur/
