Psilopterus

{{Short description|Extinct genus of birds}} {{Automatic taxobox | fossil_range = Mid Oligocene-Late Pleistocene?<ref name=Alvarengaetal2003/><ref name="Jones2017">{{Cite journal |last1=Jones |first1=W. |last2=Rinderknecht |first2=A. |last3=Alvarenga |first3=H. |last4=Montenegro |first4=F. |last5=Ubilla |first5=M. |year=2017 |title=The last terror birds (Aves, Phorusrhacidae): new evidence from the late Pleistocene of Uruguay |journal=Paläontologische Zeitschrift |volume=92 |issue=2 |pages=365–372 |doi=10.1007/s12542-017-0388-y |s2cid=134344096}} Note: their date of 96 thousand years BP is the maximum age, obtained from the bottom of the fossil-containing stratum.</ref> (Deseadan-Lujanian) ~{{fossil range|29.0|0.1}} | image = Psilopterus AMNH.jpg | image_caption = Skull of ''P. lemoinei'' in American Museum of Natural History | taxon = Psilopterus | authority = Moreno & Mercerat, 1891<ref name=Morenoetal1891/> | subdivision_ranks = Species | subdivision_ref = <ref name=Alvarengaetal2003/> | subdivision = * ''P. bachmanni'' (Moreno & Mercerat, 1891)<ref name=Morenoetal1891/> (type)<ref name=Richmond1902/> * ''P. lemoinei'' (Moreno & Mercerat, 1891)<ref name=Morenoetal1891/> * ''P. affinis'' (Ameghino, 1899)<ref name=Ameghino1899/> * ''P. colzecus'' Tonni & Tambussi, 1988<ref name=Tonnietal1988/> | synonyms = * ''Pelecyornis'' Ameghino, 1891<ref name=Alvarengaetal2003/> * ''Staphylornis'' Mercerat, 1897<ref name=Alvarengaetal2003/> }}

'''''Psilopterus''''' (Greek for "bare wing") is an extinct genus of phorusrhacid ("terror bird") from the Middle Oligocene to possibly the Late Pleistocene of Argentina and Uruguay. 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 {{convert|70|-|80|cm|ft|sp=us}} in height<ref name="Richmond1902" /> and weighed about {{convert|5|kg|lb}}, while the largest members of the genus were only about {{convert|8|kg|lb|sp=us}}.<ref name=":0">{{Cite journal |last1=DEGRANGE |first1=FEDERICO J. |last2=TAMBUSSI |first2=CLAUDIA P. |date=2011 |title=Re-Examination of Psilopterus Lemoinei (Aves, Phorusrhacidae), A Late Early Miocene Little Terror Bird from Patagonia (Argentina) |journal=Journal of Vertebrate Paleontology |volume=31 |issue=5 |pages=1080–1092 |doi=10.1080/02724634.2011.595466 |issn=0272-4634 |jstor=41407663 |bibcode=2011JVPal..31.1080D |s2cid=86790415}}</ref> The birds resemble the modern cariama (''Cariama cristata''), except with a heavier build and considerably smaller wings.<ref name="Alvarengaetal2003">{{Cite journal |last1=Alvarenga |first1=Herculano M. F. |last2=Höfling, Elizabeth |year=2003 |title=Systematic Revision of the Phorusrhacidae (Aves: Ralliformes) |journal=Papéis Avulsos de Zoologia |volume=43 |issue=4 |pages=55–91 |doi=10.1590/S0031-10492003000400001 |issn=0031-1049 |doi-access=free}}</ref> Fossil finds in Uruguay indicate the genus may have survived until 96,040 ± 6,300 years ago, millions of years after the larger phorusrhacids became extinct.<ref name="Jones2017" />

== Description and taxonomy == The most recent systematic revision of Phorusrhacidae placed ''Psilopterus'' within the subfamily Psilopterinae, along with the genera ''Procariama'' and ''Paleopsilopterus'', and divided ''Psilopterus'' into four species.<ref name=Alvarengaetal2003/>

=== ''Psilopterus bachmanni'' === ''Psilopterus bachmanni'' (Moreno & Mercerat, 1891)<ref name="Morenoetal1891">{{Cite journal |last1=Moreno |first1=Francisco P. |last2=Mercerat, Alcides |year=1891 |title=Catálogo de los pájaros fósiles de la República Argentina conservados en el Museo de La Plata |journal=Anales del Museo de la Plata |language=es |volume=1 |pages=7–71}}</ref> 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 lectotype MLP-168 is a tarsometatarsus). Other material assigned the species includes additional leg bones that are probably from the same bird,<ref name="Richmond1902">{{Cite journal |last=Richmond |first=Charles W. |year=1902 |title=List of generic terms proposed for birds during the years 1890 to 1900, inclusive, to which are added names omitted by Waterhouse in his 'Index generum avium' |url=https://www.biodiversitylibrary.org/part/53109 |journal=Proceedings of the United States National Museum |volume=24 |issue=1267 |pages=663–730 |doi=10.5479/si.00963801.1267.663 |hdl-access=free |hdl=2027/coo.31924090189725}}</ref> and an almost complete skeleton (PUM-15.904)<ref name="Sinclairetal1932">{{Cite journal |last1=Sinclair |first1=W. |last2=Farr, M. |year=1932 |title=Aves of the Santa Cruz beds |journal=Reports of the Princeton University Expeditions to Patagonia (1896–1899) |volume=7 |pages=157–191}}</ref> The material is from several sites in the Santa Cruz Formation 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; similar to the mesembriornithine phorusrhacids)<ref name=Alvarengaetal2003/> 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.<ref name=Sinclairetal1932/>

Synonyms:<ref name="AlvarengaBrodKorb">Per Alvarenga & Höfling (2003), who rely on Brodkorb (1967).</ref> * ''Psilopterus bachmanni'' (Moreno & Mercerat, 1891) * ''Patagornis 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,<ref name="Brodkorb1967">{{Cite journal |last=Brodkorb |first=Pierce |year=1967 |title=Catalogue of fossil birds, Part III (Ralliformes, Ichthyornithiformes, Charadriiformes) |journal=Bulletin of Florida State Museum |volume=2 |pages=99–220}}</ref> but the incomplete foot bone (tarsometatarsus) is indistinguishable from ''P. bachmanni''.<ref name=Alvarengaetal2003/>

=== ''Psilopterus lemoinei'' === [[File:Psilopterus.jpg|thumb|Life restoration of ''P. lemoinei'']] ''Psilopterus lemoinei'' (Moreno & Mercerat, 1891)<ref name=Morenoetal1891/> is contemporaneous with ''P. bachmanni'' and likely filled a very similar ecological niche, though ''P. lemoinei'' is slightly larger, with an estimated weigh approaching {{convert|8|kg|lb}}.<ref name=":0" /> The species is defined by part of a lower leg bone (the lectotype, MLP-162, is the distal end of a tibiotarsus), but a wide variety of material has been referred to the taxon.<ref name=Sinclairetal1932/> This material has been found at a number of sites in the Monte León and Santa Cruz Formations 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).<ref name=Sinclairetal1932/> 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.<ref name=Alvarengaetal2003/>

Synonyms:<ref name=AlvarengaBrodKorb/> * ''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'')

=== ''Psilopterus affinis'' === ''Psilopterus affinis'' (Ameghino, 1899)<ref name="Ameghino1899">{{Cite journal |last=Ameghino |first=Florentino |year=1899 |title=Sinopsis geológico-paleontológica, Suplemento (Adiciones y correciones) |language=es |journal=La Plata |page=9 |url=https://www.bfa.fcnym.unlp.edu.ar/catalogo/doc_num.php?explnum_id=3946 }}</ref> is the most poorly known species of terror bird, represented only by part of a leg bone (tarsometatarsus, MACN-A-52-184) which indicates the bird was very close to ''P. bachmanni'' in size. ''P. affinis'' is one of several species known from fragmentary material found in 1899 in the Chubut Province of Argentina (Patagonia), in rocks which dated to the Middle to Late Oligocene (Deseadan).<ref name=Ameghino1899/> Additional specimens might help clarify the taxonomy of the four apparently unrelated species.<ref name=Alvarengaetal2003/> ''P. affinis'' was originally assigned to the genus ''Phororhacos'' (''lapsus calami'' of ''Phorusrhacos'') despite the difference in size,<ref name=Ameghino1899/> and is distinguished from ''P. bachmanni'' by a groove on the leg bone.<ref name=Alvarengaetal2003/> Bertelli et al. kept this species in ''Phororhacos''.<ref name="FWBertelli">[http://www.fossilworks.org/cgi-bin/bridge.pl?a=displayTaxonomicData&reference_no=25131&display=opinions Taxonomic opinions tied to S. Bertelli et al. 2007] at Fossilworks.org</ref> Brodkorb assigned the species to ''Andrewsornis'' in 1967,<ref name=Brodkorb1967/> but this is no longer considered accurate.<ref name=Alvarengaetal2003/>

=== ''Psilopterus colzecus'' === {{multiple image |align = right | direction = horisontal |total_width = 400

|image1 = Cranial view of Psilopterus colzecus tarsometatarsus.png | alt1 =

|image2 = Caudal view of Psilopterus colzecus tarsometatarsus.png | alt2 =

|image3 = Distal view of Psilopterus colzecus tarsometatarsus.png | alt3 =

|footer = ''P. colzecus'' tarsometatarsus from the front, back, and below }}

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 (holotype MLP-76-VI-12-2), the species is defined by a groove in the front of the thigh bone (trochlea). The elements were found in the Arroyo Chasicó Formation in Buenos Aires Province of Argentina and are dated to the Late Miocene (Chasicoan).<ref name="Tonnietal1988">{{Cite journal |last1=Tonni |first1=Eduardo P. |last2=Tambussi, Claudia |year=1988 |title=Un nuevo Psilopterinae (Aves: Ralliformes) del Mioceno tardio de la Provincia de Buenos Aires, Republica Argentina |journal=Ameghiniana |language=es |volume=25 |pages=155–160}}</ref>

== Classification == When ''P. bachmanni'' was originally described in 1891, few other birds now known as Phorusrhacids were described, but when Moreno & Mercerat named the taxon, they assigned ''Psilopterus'' (then ''Patagornis'') ''bachmanni'' to a group with ''Phorusrhacos, Mesembriornis,'' and ''Stereornis,'' though the latter is now seen as a synonym of ''Phorusrhacos,''<ref>Brodkorb, P. (1967). ''Catalogue of fossil birds: part 3 (Ralliformes, Ichthyornithiformes, Charadriiformes)''. University of Florida.</ref><ref name="Alvarengaetal2003" /> that they named Stereornithidae.<ref name="Morenoetal1891" /> Since then, ''Psilopterus'' was considered the ancestor of larger Phorusrhacids like ''Mesembriornis'' and the modern ''Cariama.''<ref>Rovereto, C. (1914). Los estratos araucanos y sus fósiles. An. del Mus. ''Nac. Hist. Nat. Buenos Aires'', ''25''.</ref> In 1927, ''Psilopterus'' was placed in its own family and subfamily, Psilopterinae,<ref>Dolgopol de Saez, M. (1927). Las aves corredoras fósiles del Santacrucense. In ''Anales de la Sociedad Científica Argentina'' (Vol. 103, pp. 145-64).</ref> and later recognized as being in its own family sometimes grouped with other Phorusrhacids like ''Palaeopsilopterus'' and ''Procariama.''<ref name="Alvarengaetal2003" /> However, in the phylogenetic analysis by Degrange et al. (2015), ''Psilopterus'' was found as the only psilopterine,<ref name="phylo">{{Cite journal |last1=Degrange |first1=Federico J. |last2=Tambussi |first2=Claudia P. |last3=Taglioretti |first3=Matías L. |last4=Dondas |first4=Alejandro |last5=Scaglia |first5=Fernando |date=2015-03-04 |title=A new Mesembriornithinae (Aves, Phorusrhacidae) provides new insights into the phylogeny and sensory capabilities of terror birds |journal=Journal of Vertebrate Paleontology |volume=35 |issue=2 |article-number=e912656 |doi=10.1080/02724634.2014.912656 |bibcode=2015JVPal..35E2656D |hdl=11336/38650 |issn=0272-4634 |s2cid=85212917|hdl-access=free }}</ref> though a 2024 study reclassified ''Procariama'' as a psilopterine.<ref>{{cite journal |last1=LaBarge |first1=T. W. |last2=Gardner |first2=J. D. |last3=Organ |first3=C. L. |year=2024 |title=The evolution and ecology of gigantism in terror birds (Aves, Phorusrhacidae) |journal=Proceedings of the Royal Society B: Biological Sciences |volume=291 |issue=2021 |at=20240235 |doi=10.1098/rspb.2024.0235 |pmid=38654650 |pmc=11040249 }} [https://rs.figshare.com/articles/journal_contribution/S1_Text_from_The_evolution_and_ecology_of_gigantism_in_terror_birds_Aves_Phorusrhacidae_/25546651?backTo=/collections/Supplementary_material_from_The_evolution_and_ecology_of_gigantism_in_terror_birds_Aves_Phorusrhacidae_/7165777 Supplementary Information]</ref> 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 ''Psilopterus'' as the only member of Psilopterinae as a sister clade to Mesembriornithinae.<ref name="phylo"/>

thumb|Restoration of ''P. bachmanni'' {{clade|{{clade |1=Cariamidae |label2=Phorusrhacidae |2={{clade |1={{clade |label1=Mesembriornithinae |1={{clade |1=''Mesembriornis incertus'' |2={{clade |1=''Mesembriornis milneedwardsi'' |2={{clade |1=''Llallawavis scagliai'' |2=''Procariama simplex'' }}}}}} |label2=Psilopterinae |2={{clade |1={{clade |1='''''Psilopterus affinis''''' |2='''''Psilopterus bachmanni''''' }} |2={{clade |1='''''Psilopterus colzecus''''' |2='''''Psilopterus lemoinei''''' }}}}}} |2={{clade |1=''Kelenken guillermoi'' |2={{clade |1=''Devincenzia pozzi'' |2={{clade |1=''Titanis walleri'' |2={{clade |1=''Paraphysornis brasiliensis'' |2={{clade |1=''Andrewsornis abbotti'' |2=''Andalgalornis steulleti'' |3=''Patagornis marshi'' |4=''Phorusrhacos longissimus'' |5=''Physornis fortis'' }}}}}}}}}}}}}}|style=font-size:85%;line-height:85%|label1=Cariamiformes}}

== Paleobiology == 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. Like modern seriemas, psilopterines like ''Psilopterus'' would have fed on smaller animals based on their osteological traits.<ref name=oldest>{{Cite journal|last1=Acosta Hospitaleche |first1=C. |last2=Jones |first2=W. |year=2024 |title=Insights on the oldest terror bird (Aves, Phorusrhacidae) from the Eocene of Argentina |journal=Historical Biology: An International Journal of Paleobiology |volume=37 |issue=2 |pages=391–399 |doi=10.1080/08912963.2024.2304592 |s2cid=267475903 }}</ref> It has been also suggested that, in contrast to the other larger terror birds, ''Psilopterus'' may have been able to fly,<ref name=Tonnietal1988/> probably in a brief and clumsy manner like that of extant seriemas,<ref>{{cite book|author1=Degrange, F.J.|author2=Noriega, J.I.|author3=Areta, J.I.|year=2012|chapter=9. Diversity and paleobiology of the santacrucian birds|title=Early Miocene Paleobiology in Patagonia: high-latitude paleocommunities of the Santa Cruz Formation|editor1=Vizcaíno, S.F.|editor2=Kay, R.F.|editor3=Bargo, M.S.|pages=138–155|publisher=Cambridge University Press|location=Cambridge|doi=10.1017/CBO9780511667381.010|isbn=978-0-521-19461-7}}</ref> with body mass estimates and hind limb proportions of psilopterines being similar to those of certain birds like ''Psophia'' and ''Otis'' which often walk but are able to run and fly.<ref>{{cite journal|author1=Degrange, F.J.|year=2015|title=Hind limb morphometry of terror birds (Aves, Cariamiformes, Phorusrhacidae): functional implications for substrate preferences and locomotor lifestyle|journal=Earth and Environmental Science Transactions of the Royal Society of Edinburgh|volume=106|issue=4|pages=257–276|doi=10.1017/S1755691016000256|bibcode=2015EESTR.106..257D |hdl=11336/44728|hdl-access=free}}</ref> It is likely that psilopterines would have more preferred to run than fly, and that they would have utilized flight to reach the treetops for nesting and protection against predators.<ref name=oldest/>

== Paleoenvironment == ''Psilopterus bachmanni'' and ''lemoinei'' lived during the middle Miocene in the Santa Cruz Formation, which preserves mostly a coastal environment, but also forested and grassland regions.<ref name=":1">{{Cite book |last1=Croft |first1=D. A. |url=https://archive.org/details/hornedarmadillos0000crof |title=Horned armadillos and rafting monkeys: the fascinating fossil mammals of South America |last2=Simeonovski |first2=V. |date=2016 |publisher=Indiana University Press |isbn=978-0-253-02084-0 |series=Life of the past |location=Bloomington (Ind.) |pages=[https://archive.org/details/hornedarmadillos0000crof/page/119 119]-121 |url-access=registration}}</ref> The area had little rainfall, so forests developed around lakes and rivers, giving Santa Cruz a diverse environment. During the Miocene, the climate was similar to those of the coasts of Chile with semi-temperate forests and oceanic winds. Grasslands began spreading into Argentina during the Miocene, though much of inner Patagonia was still arid with small rainforests in between.<ref name=":2">{{Cite journal |last1=Townsend |first1=K. E. B. |last2=Croft |first2=D. A. |date=2008 |title=Diets of notoungulates from the Santa Cruz Formation, Argentina: new evidence from enamel microwear |url=https://www.researchgate.net/publication/249023462 |journal=Journal of Vertebrate Paleontology |volume=28 |issue=1 |pages=217–230 |doi=10.1671/0272-4634(2008)28[217:DONFTS]2.0.CO;2 |issn=0272-4634 |jstor=30126346}}</ref><ref name=":1" /> Large, herbivorous, South American notoungulate mammals like the toxodontids ''Nesodon'' and ''Adinotherium'' were the large low browsers, with rabbit-like interatheriiid ''Protypotherium'' being frugivorous.<ref name=":2" /> Both mammalian and avian carnivores inhabited the area, the largest being the phorusrhacid ''Phorusrhacos.'' Marsupials also lived in the region, including the large carnivorous sparassodont ''Borhyaena.''<ref name=":1" /> ''Psilopterus lemoinei'' is also known from the coastal Monte Leon Formation that was in the same region in Santa Cruz, but part of the older lower Miocene age.<ref name="auto">{{Cite journal |last1=Cuitiño |first1=J. I. |last2=Fernicola |first2=J. C. |last3=Raigemborn |first3=M. S. |last4=Krapovickas |first4=V. |date=2019 |title=Stratigraphy and depositional environments of the Santa Cruz Formation (early–middle Miocene) along the Río Santa Cruz, southern Patagonia, Argentina |url=http://www.peapaleontologica.org.ar/index.php/peapa/article/view/294 |journal=Publicación Electrónica de la Asociación Paleontológica Argentina |volume=19 |issue=2 |pages=14–33 |doi=10.5710/PEAPA.27.07.2019.294 |doi-access=free|hdl=11336/110039 |hdl-access=free }}</ref><ref>{{Cite journal |last1=Kay |first1=Richard F. |last2=Vizcaíno |first2=Sergio F. |last3=Bargo |first3=M. Susana |last4=Spradley |first4=Jackson P. |last5=Cuitiño |first5=José I. |date=2021-08-01 |title=Paleoenvironments and paleoecology of the Santa Cruz Formation (early-middle Miocene) along the Río Santa Cruz, Patagonia (Argentina) |journal=Journal of South American Earth Sciences |language=en |volume=109 |article-number=103296 |doi=10.1016/j.jsames.2021.103296 |bibcode=2021JSAES.10903296K |issn=0895-9811 |s2cid=233693434|doi-access=free }}</ref> Monte Leon preserved more mudstone and estuarine sediments, but with a very similar fauna to the Santa Cruz Formation as the two formations had a direct transition.<ref name="auto" />

== References == {{Portal|Argentina|Birds|Paleontology}} {{Reflist}}

== External links == * [https://www.biolib.cz/en/taxon/id470060/ Genus Taxonomy]

Category:Phorusrhacidae Category:Extinct flightless birds Category:Oligocene birds Category:Paleogene birds of South America Category:Miocene birds of South America Category:Deseadan Category:Santacrucian Category:Chasicoan Category:Huayquerian Category:Montehermosan Category:Oligocene Argentina Category:Pleistocene Argentina Category:Fossils of Argentina Category:Oligocene Uruguay Category:Pleistocene Uruguay Category:Fossils of Uruguay Category:Fossil taxa described in 1891