Patagornis is a genus of extinct flightless predatory birds of the family Phorusrhacidae. Known as "terror birds", these lived in what is now Argentina during the Early and Middle Miocene; the Santa Cruz Formation in Patagonia contains numerous specimens. Patagornis was an agile, medium sized Patagornithine and was likely a pursuit predator. Etymology The genus name means "bird from Patagonia" after the location the fossils were found in and the species name after prominent American paleontologist Othniel Charles Marsh, who had also named notable fossil birds but from the American West like Hesperornis and Ichthyornis. Recently, Federico Agnolin has promoted reusing Florentino Ameghino’s 1891 name Tolmodus inflatus because the name Patagornis marshi wasn’t used for over 100 years until a paper by Alvarenga & Höfling in 2003. This would make the name Patagornis marshi a nomen nudum and Tolmodus inflatus the valid name due to its frequent use. Despite this, the use of the Patagornis marshi has had a great resurgence in use in recent years and the proper nomenclature hasn't been established by the ICZN. The generic name Tolmodus means "bold tooth" due to the misinterpretation of the holotype premaxilla as the tooth of a mammal, while the species name means "inflated" due to its large size. History and taxonomy In 1891 during the "Argentine Bone Wars", a competition between Argentine paleontologists Francisco Moreno and Florentino Ameghino, the former and his colleague Alcides Mercerart described a new genus and species of phorusrhacid, Patagornis marshi, based on a mandibular symphysis that was missing the tip, though it was then thought to be a piece of the premaxilla. The fossil (MLP-143) was found alongside many other parts of a skeleton, likely from the same individual as the symphysis, including: 3 vertebrae and fragments of many others, parts of the hindlimbs, and ungues. The specific locality where these fossils were found isn't known in detail, besides that they came from the upper middle Miocene strata of the Santa Cruz Formation of Santa Cruz, Argentina. In the same paper, Moreno and Mercerat named 2 more species of Patagornis, Patagornis lemoinei and Patagornis bachmanni, based on fossils found in the Monte León Formation, Argentina in lower Miocene strata. They also named Palaeociconia cristata based on 2 vertebrae and 2 ungues from Santa Cruz, believing that they were from a fossil stork related to Ciconia. In 1933, biologist Karl Lambert placed P. cristata in its