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.

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.

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.

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.

[1] 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.

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.

[10] In the district of Tiarajú (also near São Gabriel) was found the basal anomodont Tiarajudens[11][12] From the Serra do Cadeado area (near Ortigueira, State of Paraná), come the amphibian Australerpeton,[10] an undetermined species of the dicynodont Endothiodon,[13] (possibly E. bathystoma[14]) as well as an indeterminate tapinocephalid dinocephalian showing similarities with the genera Moschops and Moschognathus.

Vertebrate fossils from the Rio do Rasto Formation occur in scattered, isolated, and discontinuous outcrops due to dense vegetation cover, making it difficult to establish local correlations.

[16][7] The broad error margin of this radiometric dating places the Brazilian dinocephalian sites in the Lower Roadian – Middle Capitanian time interval, confirming the Guadalupian age of this part of the Morro Pelado Member.

[15] 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:[1] Biarmosuchus tener Estemmenosuchus uralensis Ulemosaurus svijagensis Tapinocaninus pamelae Archaeosyodon praeventor Sinophoneus yumenensis Titanophoneus adamanteus Titanophoneus potens Anteosaurus magnificus Pampaphoneus biccai Notosyodon gusevi Syodon biarmicum Australosyodon nyaphuli During the Permian, most of the landmasses were united into a single supercontinent, Pangea, which was roughly C-shaped.

However, this bridge was probably not yet formed in the Middle Permian and marine barriers broke up the different Cathaysian blocks, making it difficult for animals to disperse from Cathaysia to Southern Africa via Eastern Europe.

[1] The discovery of probable anteosaur footprints in southern France,[N 1] which was then located at low paleolatitude, at the level of the 10th parallel north, also supports this hypothesis, the south-western Europe being in this migration corridor.