Psilopterus
Encyclopedia
Psilopterus is an extinct genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of phorusrhacid
Phorusrhacidae
Phorusrhacids , colloquially known as "terror birds" as the larger species were apex predators during the Miocene, were a clade of large carnivorous flightless birds that were the dominant predators in South America during the Cenozoic, 62–2 million years ago. They were roughly 1–3 meters tall...
("terror bird") from the Middle Oligocene
Oligocene
The Oligocene is a geologic epoch of the Paleogene Period and extends from about 34 million to 23 million years before the present . As with other older geologic periods, the rock beds that define the period are well identified but the exact dates of the start and end of the period are slightly...
to Late Miocene
Miocene
The Miocene is a geological epoch of the Neogene Period and extends from about . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene...
of Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
. 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 cm (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 (15.4 lb). The birds resemble the modern cariama
Red-legged Seriema
The Red-legged Seriema or Crested Cariama is a mostly predatory terrestrial bird in the seriema family , included in the "Gruiformes" in the old paraphyletic circumscription, but increasingly placed in a distinct order Cariamae...
(Cariama cristata), except with a heavier build and considerably smaller wings. The strong morphological
Morphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....
similarity between the claw
Claw
A claw is a curved, pointed appendage, found at the end of a toe or finger in most mammals, birds, and some reptiles. However, the word "claw" is also often used in reference to an invertebrate. Somewhat similar fine hooked structures are found in arthropods such as beetles and spiders, at the end...
s 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.
Description and taxonomy
Procariama
Procariama is an extinct Monotypic genus of giant flightless predatory birds in the family Phorusrhacidae or "terror birds" which lived in Argentina....
and Paleopsilopterus
Paleopsilopterus
Paleopsilopterus is an extinct genus of giant flightless predatory birds of the family Phorusrhacidae or "terror birds" and the subfamily of the psilopterinae that lived 60 million years ago in Brazil during the middle paleocene. The only known species is Paleopsilopterus itaboraiensis....
genera, and divided Psilopterus into four species.
P. bachmanni
Psilopterus bachmanni (Moreno & Mercerat, 1891) is the smallest species of phorusrhacid, rivaled only by P. affinis. The species (and genera) is defined by the upper portion of a fused ankle and leg bone (the lectotypeLectotype
In botanical nomenclature and zoological nomenclature, a lectotype is a kind of name-bearing type. When a species was originally described on the basis of a name-bearing type consisting of multiple specimens, one of those may be designated as the lectotype...
MLP-168 is a tarsometatarsus
Tarsometatarsus
The tarsometatarsus is a bone that is found in the lower leg of certain tetrapods, namely birds.It is formed from the fusion of several bones found in other types of animals, and homologous to the mammalian tarsal and metatarsal bones...
). Other material assigned the species includes additional leg bones that are probably from the same bird, and an almost complete skeleton (PUM-15.904) The material is from several sites in the Santa Cruz Province of Argentina dating to the Middle Miocene (Santacrucian). The most important diagnostic characteristics are a low skull and upper jaw (or maxilla
Maxilla
The maxilla is a fusion of two bones along the palatal fissure that form the upper jaw. This is similar to the mandible , which is also a fusion of two halves at the mental symphysis. Sometimes The maxilla (plural: maxillae) is a fusion of two bones along the palatal fissure that form the upper...
; similar to the mesembriornithine phorusrhacids) and the extreme slant of the front edge of the hole just before the eye (rostal portion of the antorbital fenestra), though there are also differences in the rest of the skeleton.
Synonyms:
- Psilopterus bachmanni (Moreno & Mercerat, 1891)
- PatagornisPatagornisPatagornis is an extinct genus of giant flightless predatory birds of the family Phorusrhacidae or "terror birds" that lived in Argentina....
bachmanni Moreno & Mercerat, 1891 - Psilopterus communis Moreno & Mercerat, 1891
- Psilopterus intermedius Moreno & Mercerat, 1891
- Phororhacos delicatus Amegino, 1891
Brodkorb considered Psilopterus minutus Amerghino, 1981 a separate species, but the incomplete foot bone (tarsometatarsus) is indistinguishable from P. bachmanni.
P. lemoinei
Psilopterus lemoinei (Moreno & Mercerat, 1891) is contemporaneous with P. bachmanni and likely filled a very similar ecological nicheEcological niche
In ecology, a niche is a term describing the relational position of a species or population in its ecosystem to each other; e.g. a dolphin could potentially be in another ecological niche from one that travels in a different pod if the members of these pods utilize significantly different food...
, though P. lemoinei is slightly larger, with an estimated weigh approaching 7 kilograms (15.4 lb). The species is defined by part of a lower leg bone (the lectotype, MLP-162, is the distal end of a tibiotarsus
Tibiotarsus
The tibiotarsus is the large bone between the femur and the tarsometatarsus in the leg of a bird. It is the fusion of the proximal part of the tarsus with the tibia.A similar structure also occurred in the Mesozoic Heterodontosauridae...
), but a wide variety of material has been referred to the taxon. This material has been found at a number of sites in the Santa Cruz Province of Argentina that are dated to the Middle Miocene (Santacrucian). Diagnostic characteristics include a higher skull and upper jaw (maxilla), and the front portion of the hole in front of the eyes (rostral edge of the antorbital fenestra) is less slanted. Additional differences in the remainder of the skeleton are noted in Sinclair and Farr (1932). A number of discrepancies between various specimens have been attributed to differences in age or sex, but material currently assigned to P. lemonei and P. bachmanni may be reclassified at the species level if reexamined in depth.
Synonyms:
- Patagornis lemoinei Moreno & Mercerat, 1891
- Psilopterus australis Moreno & Mercerat, 1891
- Pelecyornis tubulatus Ameghino, 1895 (synonym of Psilopterus australis)
- Phororhacos modicus Ameghino, 1895
- Staphylornis gallardoi Mercerat, 1897 (possible synonym of Psilopterus australis)
- Staphylornis erythacus Mercerat, 1897 (possible synonym of Psilopterus australis)
- Pelecyornis tenuirostris Sinclair & Farr, 1932 (synonym of Psilopterus australis)
P. affinus
Psilopterus affinus (Ameghino, 1899) is the most poorly known species of terror bird, represented only by part of a leg bone (tarsometatarsusTarsometatarsus
The tarsometatarsus is a bone that is found in the lower leg of certain tetrapods, namely birds.It is formed from the fusion of several bones found in other types of animals, and homologous to the mammalian tarsal and metatarsal bones...
, MACN-A-52-184) which indicates the bird was very close to P. bachmanni in size. P. affinus is one of several species known from fragmentary material found in 1899 in the Chubut Province
Chubut Province
Chubut a province in the southern part of Argentina situated between the 42nd parallel south and the 46th parallel south , the Andes range separating Argentina from Chile, and the Atlantic ocean...
of Argentina (Patagonia
Patagonia
Patagonia is a region located in Argentina and Chile, integrating the southernmost section of the Andes mountains to the southwest towards the Pacific ocean and from the east of the cordillera to the valleys it follows south through Colorado River towards Carmen de Patagones in the Atlantic Ocean...
), in rocks which dated to the Middle to Late Oligocene (Deseadan). Additional specimens might help clarify the taxonomy of the four apparently unrelated species. P. affinus was originally assigned to the Phororhacos genus despite the difference in size, and is distinguished from P. bachmanni by a groove on the leg bone. Brodkorb assigned the species to Andrewsornis
Andrewsornis
Andrewsornis is an extinct genus of giant flightless predatory birds of the family Phorusrhacidae or "terror birds" that lived in Argentina....
in 1967, but this is no longer considered accurate.
P. colzecus
The most recently discovered species in the genus, Psilopterus colzecus Tonni & Tambussi, 1988, is similar to P. lemoinei in size. Known only from a single incomplete skeleton that includes parts of the jaw, arm, and leg (holotypeHolotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
MLP-76-VI-12-2), the species is defined by a groove in the front of the thigh bone (trochlea
Trochlea
Trochlea is a term in anatomy. It refers to a grooved structure reminiscent of a pulley's wheel.Most commonly, trochleae bear the articular surface of saddle and other joints:* Trochlea of humerus* Trochlear process of the Calcaneus...
). The elements were found in the Buenos Aires Province
Buenos Aires Province
The Province of Buenos Aires is the largest and most populous province of Argentina. It takes the name from the city of Buenos Aires, which used to be the provincial capital until it was federalized in 1880...
of Argentina and are dated to the Late Miocene (Chasicóan).