phylogenetic analysis in 2015 by Degrange et al found Patagornis in a merged Phorusrhacinae and in polytomy with Physornis and Phorusrhacos as well. 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 Patagornis as a member of a large clade that includes Physornis, Phorusrhacos and Andalgalornis, among others. Paleoenvironment Patagornis lived during the middle Miocene in the Santa Cruz Formation, which preserves mostly a coastal environment, but also forested and grassland regions. The area had little rainfall, so forests developed around lakes and rivers, giving Santa Cruz a diverse environment. During the Miocene, the climate was similar to those of the coasts of Chile with semi-temperate forests and oceanic winds. Grasslands began spreading into Argentina during the Miocene, though much of inner Patagonia was still arid with small rainforests in between. Large, herbivorous, South American notoungulate mammals like the Toxodonts Nesodon and Adinotherium were the large low browsers, with rabbit-like Interathere Protypotherium being frugivorous. Both mammalian and avian carnivores inhabited the area, the largest being the Phorusrhacid Phorusrhacos. Marsupials also lived in the region, including the large carnivorous Sparassodont Borhyaena. Patagornis is also known from the coastal Monte Leon Formation that was in the same region in Santa Cruz, but part of the older lower Miocene age. Monte Leon preserved more mudstone and estuarine sediments, but with a very similar fauna to the Santa Cruz Formation as the two formations had a direct transition. References External links Genus Taxonomy Phorusrhacidae Extinct flightless birds Miocene birds of South America Laventan Colloncuran Friasian Santacrucian Neogene Argentina Fossils of Argentina Fossil taxa described in 1891