Estemmenosuchid
| Estemmenosuchidae Temporal range: Wordian |
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| Life restoration of Estemmenosuchus mirabilis | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Order: | Therapsida |
| Suborder: | †Dinocephalia |
| Clade: | †Tapinocephalia |
| Family: |
†Estemmenosuchidae Tchudinov, 1960 |
Estemmenosuchidae is a family of large, very early herbivorous therapsids that flourished during the Middle Permian period. They are distinguished by horn-like structures, probably for display or agonistic behavior. Apart from the best known genus, Estemmenosuchus, the group is poorly known. To date, their fossils are known only from the Perm region of Russia (a region referred to by Russian paleontologists as the Cis-Urals).
Estemmenosuchids are among the most distinctive of the Permian tetrapods. The high and massive skull is equipped with a number of horns projecting both upwards and outwards, which were probably used for intra-specific display. The incisors and canine teeth are large, but those at the side are reduced, with a serrated apex, and may have helped to break up plant material, although they were too small to be of much use. The body is large and bulky, indicating a large digestive tract for digesting volumes of plant food. The skull superficially resembles that of Styracocephalus, but the "horns" are formed from different bones.
Estemmenosuchids belong to the Dinocephalian group, a group of early, primitive, but diverse therapsids – often of large size – that are known only from the Middle Permian period. They are however far more primitive and unspecialised than the better known dinocephalians of the South African Karoo (Beaufort Group), and mostly lived somewhat earlier. They are also unusual in that, despite their primitive nature and early date of appearance, they show herbivorous adaptations.
Because of this, there have been two main interpretations of their evolutionary relationships with other Dinocephalia.
Hopson and Barghusen in 1986, who provided the first cladistic study of the Therapsida, coined the term Tapinocephalia for herbivorous dinocephalians, as opposed to the "Anteosauria" for the carnivorous forms. They suggested that Estemmenosuchids are very early/primitive members of the Tapinocephalia.
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