Name: Psilopterus ‭(‬Bare wing‭)‬.
Phonetic: Cy-lop-teh-rus.
Named By: Francisco P.‭ ‬Moreno‭ & ‬Alcides Mercerat‭ ‬-‭ ‬1891.
Synonyms: Patagornis bachmanni,‭ ‬P.‭ ‬lemoinei,‭ ‬Pelecyornis tubulatus,‭ ‬Phororhacos delicatus,‭ ‬P.‭ ‬modicus,‭ ‬Psilopterus australis,‭ ‬P.‭ ‬communis,‭ ‬P.‭ ‬intermedius‭ ‬-‭ *‬note,‭ ‬other synonyms may actually exist and this list should not be assumed to be complete.
Classification: Chordata,‭ ‬Aves,‭ ‬Cariamae,‭ ‬Phorusrhacidae,‭ ‬Psilopterinae.
Species: P.‭ ‬bachmani‭ (‬type‭)‬,‭ ‬P.‭ ‬affinis,‭ ‬P.‭ ‬colzecus,‭ ‬P.‭ ‬lemoinei.
Diet: Carnivore.
Size: From‭ ‬70-80‭ ‬centimetres,‭ ‬up to just under a metre tall,‭ ‬depending upon species.‭ ‬Weight estimated between‭ ‬5‭ ‬and‭ ‬7‭ ‬kilograms,‭ ‬again depending upon the size of the species.
Known locations: Argentina.
Time period: Mid Oligocene through to late Miocene.
Fossil representation: Many specimens,‭ ‬but often of fragmentary remains.

       Being one of the smallest members of the Phorusrhacidae,‭ ‬Psilopterus was no way near the scale of the larger phorusrhacids like Brontornis.‭ ‬However the exact size of Psilopterus is something that is hard to be certain about as not only do estimates depend upon the specific species,‭ ‬but there is an outside chance that material referred to the smallest‭ (‬P.‭ ‬bachmani‭) ‬and largest‭ (‬P.‭ ‬lemionei‭) ‬species may actually represent the same genus.‭ ‬Clarification of this matter is not helped by the fact that most Psilopterus remains are of fragmentary fossil material,‭ ‬a problem caused by the hollow light weight bones typical to birds that get damaged easily during fossilization.‭ ‬Also many of the species once assigned to Psilopterus have now be found to represent other older species,‭ ‬as well as additional material from other genera being reassigned to Psilopterus as well.
       The‭ ‘‬terror bids‭’ ‬of the Phorusrhacidae are often compared to the extant seriema birds of South America‭ (‬Cariama cristata and Chunga burmeisteri‭)‬,‭ ‬and out of all the phorusrhacids,‭ ‬Psilopterus is closest to the seriema in physical size.‭ ‬This would suggest similar hunting behaviour where Psilopterus’s preferred prey would be invertebrates such as large insects and small vertebrates like lizards,‭ ‬frogs and small rodents.‭ ‬Psilopterus may have also had a similar feeding style where small prey would be thrown against the ground and hard objects to stun and kill the prey as well as break its bones for easier swallowing.‭ ‬The long legs of Psilopterus would have allowed it to peer down into the undergrowth from above where prey could be more easily spotted,‭ ‬as well as providing a good turn of speed for avoiding other larger predators.‭

Further reading
- Catalogue des Oiseaux Fossiles de la Republique Argentine conserves au Musee de la Plata. - Anales del Museo de la Plata 1:1-71. - F. P. Moreno & A. Mercerat - 1891.
- Systematic Revision of the Phorusrhacidae (Aves: Ralliformes). - Papéis Avulsos de Zoologia. 43 (4): 55–91. - Herculano M. F. Alvarenga & Elizabeth Höfling - 2003.


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