''Physornis'' is an

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

genus of giant flightless predatory birds of the family Phorusrhacidae or "terror birds", most closely related to '' Paraphysornis'', that lived in Argentina. The type species is ''P. fortis''. It lived during the Middle to Late Oligocene (

Deseadan The Deseadan ( es, Deseadense) age is a period of geologic time (29.0–21.0 Ma) within the Oligocene epoch of the Paleogene to the Early Miocene epoch of the Neogene, used more specifically within the SALMA classification of South America. It fo ...

). Few fossils are known, but the available material suggests that ''Physornis'' was one of the largest phorusrhacids.

History and taxonomy

The holotype of ''Physornis'' ( BMNH-A583) is a 137 mm long portion of a symphysis and the right branch of this lower jaw, described in 1894 by paleontologist Florentino Ameghino. He published the name, together with a description but without a drawing, in the same year.Brodkorb, P. (1967). ''Catalogue of fossil birds: part 3 (Ralliformes, Ichthyornithiformes, Charadriiformes)''. University of Florida.Alvarenga, H. M., & Höfling, E. (2003). Systematic revision of the Phorusrhacidae (Aves: Ralliformes). ''Papéis Avulsos de Zoologia'', ''43''(4), 55-91. The fossil was collected from the

Oligocene The Oligocene ( ) is a geologic epoch of the Paleogene Period and extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that define the epoch are well identified but the ...

layers of

Santa Cruz Province Santa Claus, also known as Father Christmas, Saint Nicholas, Saint Nick, Kris Kringle, or simply Santa, is a legendary figure originating in Western Christian culture who is said to bring children gifts during the late evening and overnigh ...

, Argentina and the

era SALMA, making it one of the older known phorusrhacid species. The type specimen of ''Physornis fortis'' is very fragmetary and besides the type symphysis has virtually no other characteristics, and this has caused the validity of the species to come into question.Patterson, B. (1941). A new phororhacoid bird from the Deseado formation of Patagonia.

Ornithologist Ornithology is a branch of zoology that concerns the "methodological study and consequent knowledge of birds with all that relates to them." Several aspects of ornithology differ from related disciplines, due partly to the high visibility and th ...

and paleontologist Bryan Patterson suggested that the type specimen could be from the pelvis of a mammal, claiming that it is a ''

nomen dubium In binomial nomenclature, a ''nomen dubium'' (Latin for "doubtful name", plural ''nomina dubia'') is a scientific name that is of unknown or doubtful application. Zoology In case of a ''nomen dubium'' it may be impossible to determine whether a s ...

''. 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'', though the latter has since been suggested to be a galliform.Agnolin, F. L. (2021)
Reappraisal on the Phylogenetic Relationships of the Enigmatic Flightless Bird (Brontornis burmeisteri) Moreno and Mercerat, 1891.
''Diversity'', ''13''(2), 90. Florentino Ameghino named another genus and species of phorusrhacid in 1898, ''Aucornis eurhynchus,'' based on a partial

mandibular symphysis In human anatomy, the facial skeleton of the skull the external surface of the mandible is marked in the median line by a faint ridge, indicating the mandibular symphysis (Latin: ''symphysis menti'') or line of junction where the two lateral halves ...

, proximal

tarsometatarsus The tarsometatarsus is a bone that is only found in the lower leg of birds and some non-avian dinosaurs. It is formed from the fusion of several bones found in other types of animals, and homologous to the mammalian tarsus (ankle bones) and meta ...

, and 3 pedal phalanges recovered from the "cretaceo de Patagonia", though these fossils most likely date to the

instead. This species has been synonymized with ''Physornis'' ''fortis'' based on the anatomy of the symphysis. 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. Brodkorb synonymized it with ''Physornis fortis'' in 1967, but it could also be synonymous with '' Andrewsornis abbotti,'' making it a ''

species inquirenda In biological classification, a ''species inquirenda'' is a species of doubtful identity requiring further investigation. The use of the term in English-language biological literature dates back to at least the early nineteenth century. The term ...

''. In 1982, Herculano Alvarenga named a new species of ''Physornis, Physornis brasiliensis,'' based on a 75% complete skeleton from the Upper Oligocene - Lower Miocene layers of São Paulo, Brazil. A decade later in 1993, Alvarenga came to the conclusion that it was actually its own genus of Phorusrhacid that he named '' Paraphysornis.''Alvarenga, H.M.F. (1993). "Paraphysornis Novo Gênero Para Physornis brasiliensis Alvarenga, 1982 (Aves:Phorusrhacidae)". Anais da Academia Brasileira de Ciências. 65 (4): 403–406.

Description

''Physornis'' has been referred to the Brontornithinae subfamily, the largest and most solidest shock birds, though '' Brontornis'' itself is likely not a Phorusrhacid. ''Physornis'' probably had a huge size, possibly even approaching to that of ''Brontornis''. The Symphysis Mandibulae is remarkably short and wide and has a characteristic ventral surface in the middle section. The lateral edge of the Hypotarsus is, seen from behind, an excellent comb that clearly distinguishes the genus ''Paraphysornis'' and ''Brontornis''. The lateral cotyle of the

is almost square when it is seen from close by.

Classification

Ameghino originally classified ''Physornis'' with his taxa ''Phorusrhacos'' and '' Tolmodus,'' though in years since it has also been classified closest to '' Brontornis'' and '' Paraphysornis'', the former possibly being a type of

gastornithid ''Gastornis'' is an extinct genus of large flightless birds that lived during the mid Paleocene to mid Eocene epochs of the Paleogene period. Fossils have been found in Europe, Asia and North America, with the remains from North America origina ...

or Anseriform instead.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.

References

{{Taxonbar, from=Q1617702 Brontornithinae Deseadan Fossils of Argentina Fossil taxa described in 1895 Taxa named by Florentino Ameghino Phorusrhacidae Oligocene birds Golfo San Jorge Basin Sarmiento Formation