[2][1] The fossil was collected from the Oligocene layers of Santa Cruz Province, Argentina and the Deseadan era SALMA, making it one of the older known phorusrhacid species.

[3][2] However in 2003 during their review of phorusrhacidae, Herculano Alvarenga and Elizabeth Höfling found the type symphysis to be diagnostic and from a large phorusrhacid similar to Paraphysornis and Brontornis,[1] though the latter has since been suggested to be a galliform.

[4] Florentino Ameghino named another genus and species of phorusrhacid in 1898, Aucornis eurhynchus, based on a partial mandibular symphysis, proximal tarsometatarsus, and 3 pedal phalanges recovered from the "cretaceo de Patagonia", though these fossils most likely date to the Oligocene instead.

[1][2] Another species, Aucornis solidus, was named the next year by Ameghino based on a proximal portion of a phalanx from the third toe found in the same area.

[4]The following phylogenetic tree shows the internal relationships of Phorusrhacidae under the exclusion of Brontornis as published by Degrange and colleagues in 2015, which recovers Physornis as a member of a large clade that includes Patagornis, Phorusrhacos and Andalgalornis, among others.