Pampaphoneus is an extinct genus of carnivorous dinocephalian therapsid belonging to the family Anteosauridae. It lived 268 to 265 million years ago during the Wordian age of the Guadalupian (= middle Permian) period in what is now Brazil. Pampaphoneus is known by an almost complete skull with the lower jaw still articulated, discovered on the lands of the Boqueirão Farm, near the city of São Gabriel, in the state of Rio Grande do Sul. A second specimen from the same locality was reported in 2019 and 2020 but has not yet been described. It is composed of a skull associated with postcranial remains. It is the first South American species of dinocephalian to have been described. The group was previously known in South America only by a few isolated teeth and a jaw fragment reported in 2000 in the same region of Brazil. Phylogenetic analysis conducted by Cisneros and colleagues reveals that Pampaphoneus is closely related to anteosaurs from European Russia, indicating a closer faunal relationship between South America and Eastern Europe than previously thought, thus promoting a Pangea B continental reconstruction.
Taxonomy
Etymology The name of the genus comes from the Pampas, a region of vast plains typical of southern South America, from which the specimen originates, and from the Greek phoneus, meaning "killer", in reference to the predatory habits of the animal. The specific epithet honors José Bicca, the landowner of the farm where the fossil was found.
Classification In describing Pampaphoneus, Cisneros et al. presented several cladograms confirming the recognition of the clades Anteosaurinae and Syodontinae erected a year earlier by Christian Kammerer. In all their analyzes, Pampaphoneus is identified as the most basal Syodontinae:
Description
The holotype (UFRGS PV386P) of Pampaphoneus is a skull measuring approximately 32 cm in length. As with all anteosaurs, the ventral margin of the premaxilla is inclined upwards and the postorbital bar is strongly curved anteroventrally so that the temporal fenestra undercuts orbit. The skull roof is slightly pachyostosed. The temporal fenestrae open widely on the skull roof where the insertion zone of the adductor musculature of the mandible extends to the pineal boss. The frontals contribute to the insertion zone of this musculature and also participate to the anterior edge of the pineal boss. These characteristics indicate that Pampaphoneus belongs to the clade Syodontinae. Within this group it is with the Russian species Syodon biarmicum that Pampaphoneus shares the most similarities. Like the latter, it possesses strongly recurved hook-like canines and very low postcanines with serrassions. The canines of the holotype are 7 cm in length. Pampaphoneus however differs from Syodon by its larger size, more robust snout, thickened postorbital forming a supraorbital boss, and a well-developed ridge extending from the pineal boss to the orbital rim. It also differs from other anteosaurs by its squamosal with a jugal process extending beyond the anterior edge of the temporal fenestra. Also unlike Syodon, Pampaphoneus lacked bifurcating anterior processes in its parietals. Its antorbital depression is also more gradual than in Syodon and excavates the posterior of the maxilla and the postfrontal and not just the lacrimal as it does in Syodon. A peculiarity of the holotype that was thought to be a diagnostic feature is the presence of only four teeth per premaxilla (the fourth incisor, small in size, being however laterally masked by the maxilla) and eight postcanines. However, a second skull (yet undescribed) was reported showing some differences with the holotype such as the presence of five premaxillary teeth and only seven postcanines. Since the other cranial elements are very similar, these differences are interpreted as intraspecific variation. Although being a Syodontinae, Pampaphoneus also shares several characters with the more derived Anteosaurinae. It thus has a well-developed medial crest on the skull roof, while a pronounced thickening of each postorbital forms a supraorbital boss similar to that of a subadult individual of the Russian Titanophoneus potens. In addition, the angular bone of the lower jaw bears a boss as in Anteosaurus and the two species of Titanophoneus. This angular boss is however much less developed in Pampaphoneus.
Paleoenvironment
Palaeobiogeography
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