|Named By:||Francisco P. Moreno & Alcides Mercerat in 1891|
|Time Period:||Mid Oligocene-Late Miocene (Deseadan-Montehermosan)~29.0-5.3 Ma|
|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|
|Fossil(s):||Many specimens, but often of fragmentary remains|
|Classification:||| Chordata | Aves | Cariamae | Phorusrhacidae | Psilopterinae ||
|Also known as:||| Patagornis bachmanni | Patagornis lemoinei | Pelecyornis tubulatus | Phororhacos delicatus | Phororhacos modicus | Psilopterus australis | Psilopterus communis | Psilopterus intermedius ||
Psilopterus (Greek for "bare wing") is an extinct genus of phorusrhacid ("terror bird") from the Middle Oligocene to Late Miocene of Argentina. Compared to other phorusrhacids, members of the genus are both relatively gracile and diminutive, and include the smallest known species of terror bird: with the head raised P. bachmanni was 70-80 centimeters (2.3-2.6 ft) in height and weighed about 5 kilograms (11 lb), while the largest members of the genus were only about 7 kilograms (15 lb). The birds resemble the modern cariama (Cariama cristata), except with a heavier build and considerably smaller wings. The strong morphological similarity between the claws of the predatory cariama and Psilopterus, both of which are sharp, curved, and laterally compressed, may indicate they were used to strike prey. In contrast to the other, larger terror birds, Tonni and Tambussi also suggested Psilopterus could use their claws to climb trees, and could even fly, but this has been rejected in more recent literature.