The big and small Estemmenosuchus (Dinocephalia, Therapsida, Synapsida, Archosauromorpha)

Figure 1. There are two known Estemmenosuchus species, the smaller famous one, E. mirabilis, and the larger less famous one, E. uralensis, here shown to scale. The ectopterygoid (Tr here) is oddly placed, posterior to the pterygoid, but of the standard shape, if I'm reading this drawing correctly.

Figure 1. There are two known Estemmenosuchus species, the smaller famous one, E. mirabilis, and the larger less famous one, E. uralensis, here shown to scale. The ectopterygoid (Tr here) is oddly placed in E. uralensis, posterior to the pterygoid, but of the standard shape, if I’m reading this drawing correctly. the palatine/pterygoid pads are part of the herbivorous chewing apparatus.

Earlier we looked at
the baroque skull of Estemmenosuchus (late Permian, Tchudinov 1960, 1968) here, here and here. Today they are shown together to scale, with one about twice the size of the other. E. mirabilis is the more famous one because it is the more bizarre one, yet it is smaller than E. uralenesis. Both the postfrontals and the jugals expand distally to proceed these skull ‘horns’. A smaller one is produced by the premaxillary ascending process. And other smaller bumps are produced by the postorbital and frontal.

Looking at the palate drawings
we see a row of palatine teeth, a pterygoid with a row of teeth on the transverse process and more on the medial process, and some oddly placed ectopterygoids posterior to the pterygoids.

Figure1. The skull sutures on Esttemmenosuchus mirabilis. When you score a skull for analysis, you have to have this data.

Figure3. The skull of Estemmenosuchus mirabilis, the hippopotamus of the Late Permian. Note the large procumbent teeth.

The maxilla has
two parallel rows of post canine teeth in E. mirabilis, essentially one row of marginal maxillary teeth in E. uralensis. But the maxillary/palatine row in E. uralensis is a new twist on the same construction. We’ve seen multiple rows of maxillary teeth in the taxa that lead up to rhynchosaur lepidosaurs.

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.

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