The data I have
for Estemmenosuchus comes from a well-lit by low resolution image complete with halftone dots and moire patterns (Fig. 1). Nevertheless, I think I can find sutures on the image.
Figure1. The skull sutures on Esttemmenosuchus mirabilis (PIN 1758/6). When you score a skull for analysis, you have to have this data. I think that’s the right cheekbone peeking through the naris. See how colors make this interpretation clear, whether accurate or not? The ascending process of the premaxilla look like it spreads laterally. Think of that as an option. That’s the squamosal forming the tip of the cheek horn. Yes, you can still see the moire pattern formed by the halftone dots.
Estemmenosuchus uralensis (Middle Permian, Tchudinov 1960, 1968; Holotype PIN 1758/4 Skull length: 60 cm; E. mirabilis PIN 1758/6) could be an omnivore. Considering its bulk and short thick legs, it is more likely an herbivore, like a hippo.
Estemmenosuchus skin
According to Wikipedia, “The fossil material includes an exceptionally well preserved skin impression. The skin appears to be smooth and undifferentiated with no signs of either hairs or scales but with evidence of being well supplied with glands.”
Figure 3. Estemmenosuchus cover
So I made a big mistake
back in 1991 when I illustrated Estemmenosuchus with scales on the cover of this book. The longer you linger the more you learn.
References
Tchudinov PK 1960. Diagnosen der Therapsida des oberen Perm von Ezhovo: Paleontologischeskii Zhural, 1960, n. 4, p. 81-94.
Tchudinov PK 1968. Structure of the integuments of theriomorphs. Doklady Acad. Nauk SSSR. 179:207-210.
The Pterosaur Heresies 