Temporal range: Late JurassicPresent, Earliest 165 Ma if Anchiornithidae are members
Jeholornis prima NMNS.jpg
Fossil specimen of Jeholornis prima
Common blackbird (Turdus merula)
Scientific classification e
Gauthier, 1986

Avialae ("bird wings") is a clade containing the only living dinosaurs, the birds. It is usually defined as all theropod dinosaurs more closely related to birds (Aves) than to deinonychosaurs, though alternative definitions are occasionally used (see below).

Archaeopteryx lithographica, from the late Jurassic Period Solnhofen Formation of Germany, is possibly the earliest known avialan which may have had the capability of powered flight,[2] though it might have been a deinonychosaur instead.[3] Several older (but non flight-capable) avialans are known from the late Jurassic Tiaojishan Formation of China, dated to about 160 million years ago.[4][5]


Most researchers define Avialae as branch-based clade, though definitions vary. Many authors have used a definition similar to "all theropods closer to birds than to Deinonychus."[6][7] A nearly identical definition, "the theropod group that includes all taxa closer to Passer than to Dromaeosaurus", was used by Agnolín and Novas (2013) for their clade Averaptora.[8]

Additionally, beginning in the late 2000s and early 2010s, several groups of researchers began adding the genus Troodon as an additional specifier in the definition of Avialae. Troodon had long been considered a close relative of the dromaeosaurids in the larger group Deinonychosauria, though some contemporary studies found it and other troodontids more closely related to modern birds, and so it has been specifically excluded from Avialae in more recent studies.[9]

Avialae is also occasionally defined as an apomorphy-based clade (that is, one based on derived characteristics that were not present among lineage predecessors). Jacques Gauthier, who named Avialae in 1986, re-defined it in 2001 as all dinosaurs that possessed feathered wings used in flapping flight, and the birds that descended from them.[10][11]

Differentiation from Aves

Gauthier and de Queiroz[11] (page 34) identified four conflicting ways of defining the term "Aves", which is a problem since the same biological name is being used four different ways. They proposed a solution, number 4 below, which is to reserve the term Aves only for the crown group, the last common ancestor of all living birds and all of its descendants. Other definitions of Aves found in literature were reassigned to other clade names.

  1. Aves can mean all reptiles closer to birds than to crocodiles (alternatively Avemetatarsalia [=Panaves])
  2. Aves can mean those advanced archosaurs with feathers (alternatively Avifilopluma)
  3. Aves can mean those feathered dinosaurs that can fly (alternately Avialae)
  4. Aves can mean the last common ancestor of all the currently living birds and all of its descendants (a "crown group"). (alternatively Neornithes)

Under the fourth definition Archaeopteryx is an avialan, and not a member of Aves. Gauthier's proposals have been adopted by many researchers in the field of paleontology and bird evolution, though the exact definitions applied have been inconsistent. Avialae, initially proposed to replace the traditional fossil content of Aves, is sometimes used synonymously with the vernacular term "bird" by these researchers.[9]






Jeholornis Jeholornis mmartyniuk wiki (fipped).jpg





Confuciusornis Confuciusornis sanctus mmartyniuk.png


Ornithothoraces Meyers grosses Konversations-Lexikon - ein Nachschlagewerk des allgemeinen Wissens (1908) (Antwerpener Breiftaube).jpg

Cladogram following the results of a phylogenetic study by Wang et al., 2016.[12]

The earliest known avialans come from the Tiaojishan Formation of China, which has been dated to the late Jurassic period (Oxfordian stage), about 160 million years ago.[9] The avialan species from this time period include Anchiornis huxleyi and Aurornis xui. Xiaotingia zhengi used to be considered a member, but was later classified within the clade Dromaeosauridae. The well-known Archaeopteryx dates from slightly later Jurassic rocks (about 155 million years old) from Germany. Many of these early avialans shared unusual anatomical features that may be ancestral to modern birds, but were later lost during bird evolution. These features include enlarged claws on the second toe which may have been held clear of the ground in life, and long feathers or "hind wings" covering the hind limbs and feet, which may have been used in aerial maneuvering.[13] It is also thought that early avialans were either cranially akinetic or had otherwise limited cranial kinesis.[14][15]

Avialans diversified into a wide variety of forms during the Cretaceous Period.[16] Many groups retained primitive characteristics, such as clawed wings and teeth, though the latter were lost independently in a number of avialan groups, including modern birds (Aves). While the earliest forms, such as Archaeopteryx and Jeholornis, retained the long bony tails of their ancestors,[16] the tails of more advanced avialans were shortened with the advent of the pygostyle bone in the group Pygostylia. In the late Cretaceous, around 95 million years ago, the ancestor of all modern birds also evolved a better sense of smell.[17]

The following cladogram is based on the analysis by Hartman et al. (2019), which found flight likely evolved five separate times among paravian dinosaurs, two of those among Avialae (in Scansoriopterygids and other avialans). Archaeopteryx and "anchiornithids" were placed in Deinonychosauria, Avialae's sister group.[3]





















In a study conducted in 2020, Archaeopteryx was recovered as an avialan.[18]

See also


  1. ^ a b Cau, A.; Beyrand, V.; Voeten, D.; Fernandez, V.; Tafforeau, P.; Stein, K.; Barsbold, R.; Tsogtbaatar, K.; Currie, P.; Godefroit, P. (2017). "Synchrotron scanning reveals amphibious ecomorphology in a new clade of bird-like dinosaurs". Nature. 552 (7685): 395–399. Bibcode:2017Natur.552..395C. doi:10.1038/nature24679. PMID 29211712. S2CID 4471941.
  2. ^ Alonso, P. D.; Milner, A. C.; Ketcham, R. A.; Cookson, M. J.; Rowe, T. B. (2004). "The avian nature of the brain and inner ear of Archaeopteryx" (PDF). Nature. 430 (7000): 666–669. Bibcode:2004Natur.430..666A. doi:10.1038/nature02706. PMID 15295597. S2CID 4391019. Archived from the original (PDF) on 2006-02-09. Supplementary info
  3. ^ a b Hartman, Scott; Mortimer, Mickey; Wahl, William R.; Lomax, Dean R.; Lippincott, Jessica; Lovelace, David M. (2019-07-10). "A new paravian dinosaur from the Late Jurassic of North America supports a late acquisition of avian flight". PeerJ. 7: e7247. doi:10.7717/peerj.7247. ISSN 2167-8359. PMC 6626525. PMID 31333906.
  4. ^ Hu, D.; Hou, L.; Zhang, L. & Xu, X. (2009). "A pre-Archaeopteryx troodontid theropod from China with long feathers on the metatarsus". Nature. 461 (7264): 640–643. Bibcode:2009Natur.461..640H. doi:10.1038/nature08322. PMID 19794491. S2CID 205218015.
  5. ^ Liu Y.-Q.; Kuang H.-W.; Jiang X.-J.; Peng N.; Xu H.; Sun H.-Y. (2012). "Timing of the earliest known feathered dinosaurs and transitional pterosaurs older than the Jehol Biota". Palaeogeography, Palaeoclimatology, Palaeoecology. 323–325: 1–12. Bibcode:2012PPP...323....1L. doi:10.1016/j.palaeo.2012.01.017.
  6. ^ Weishampel, David B.; Dodson, Peter; Osmólska, Halszka (eds.) (2004). The Dinosauria, Second Edition. University of California Press., 861 pp.
  7. ^ Senter, P (2007). "A new look at the phylogeny of Coelurosauria (Dinosauria: Theropoda)". Journal of Systematic Palaeontology. 5 (4): 429–463. doi:10.1017/S1477201907002143. S2CID 83726237.
  8. ^ Federico L. Agnolín & Fernando E. Novas (2013). Avian ancestors. A review of the phylogenetic relationships of the theropods Unenlagiidae, Microraptoria, Anchiornis and Scansoriopterygidae. SpringerBriefs in Earth System Sciences. pp. 1–96. doi:10.1007/978-94-007-5637-3. ISBN 978-94-007-5636-6. S2CID 199493087.
  9. ^ a b c Pascal Godefroit; Andrea Cau; Hu Dong-Yu; François Escuillié; Wu Wenhao; Gareth Dyke (2013). "A Jurassic avialan dinosaur from China resolves the early phylogenetic history of birds". Nature. 498 (7454): 359–62. Bibcode:2013Natur.498..359G. doi:10.1038/nature12168. PMID 23719374. S2CID 4364892.
  10. ^ Gauthier, J. (1986). "Saurischian monophyly and the origin of birds." In: K. Padian, ed. The origin of birds and the evolution of flight. San Francisco: California, Acad.Sci. pp.1–55. (Mem.Calif.Acad.Sci.8.)
  11. ^ a b Gauthier, J., and de Queiroz, K. (2001). "Feathered dinosaurs, flying dinosaurs, crown dinosaurs, and the name Aves." Pp. 7-41 in New perspectives on the origin and early evolution of birds: proceedings of the International Symposium in Honor of John H. Ostrom (J. A. Gauthier and L. F. Gall, eds.). Peabody Museum of Natural History, Yale University, New Haven, Connecticut, U.S.A.
  12. ^ Wang, M.; Wang, X.; Wang, Y.; Zhou, Z. (2016). "A new basal bird from China with implications for morphological diversity in early birds". Scientific Reports. 6: 19700. Bibcode:2016NatSR...619700W. doi:10.1038/srep19700. PMC 4726217. PMID 26806355.
  13. ^ Zheng, X.; Zhou, Z.; Wang, X.; Zhang, F.; Zhang, X.; Wang, Y.; Wei, G.; Wang, S.; Xu, X. (2013). "Hind Wings in Basal Birds and the Evolution of Leg Feathers". Science. 339 (6125): 1309–1312. Bibcode:2013Sci...339.1309Z. CiteSeerX doi:10.1126/science.1228753. PMID 23493711. S2CID 206544531.
  14. ^ Wang, M.; Stidham, T.A.; Li, Z.; Xu, X.; Zhou, Z. (2021). "Cretaceous bird with dinosaur skull sheds light on avian cranial evolution". Nature Communications. 12: 3890. doi:10.1038/s41467-021-24147-z.
  15. ^ Hu, H.; Sansalone, G.; Wroe, S.; McDonald, P.G.; O'Connor, J.K.; Li, Z.; Xu, X; Zhou, Z. (2019). "Evolution of the vomer and its implications for cranial kinesis in Paraves". PNAS. 116 (39): 19571–19578. doi:10.1073/pnas.1907754116.
  16. ^ a b Chiappe, Luis M. (2007). Glorified Dinosaurs: The Origin and Early Evolution of Birds. Sydney: University of New South Wales Press. ISBN 978-0-86840-413-4.
  17. ^ Agency France-Presse (13 April 2011). "Birds survived dino extinction with keen senses". Cosmos Magazine. Archived from the original on 2 April 2015. Retrieved 11 June 2012.
  18. ^ Cau, Andrea (2020-02-25). "The body plan of Halszkaraptor escuilliei (Dinosauria, Theropoda) is not a transitional form along the evolution of dromaeosaurid hypercarnivory". PeerJ. 8: e8672. doi:10.7717/peerj.8672. ISSN 2167-8359. PMC 7047864. PMID 32140312.

Media files used on this page

Ichthyornis restoration.jpeg
Author/Creator: El fosilmaníaco, Licence: CC BY-SA 4.0
Life restoration of Ichthyornis dispar, a primitive seabird that lived in the Western Interior Seaway (North America)during the Late Cretaceous.
Mononykus Restoration.png
Author/Creator: PaleoNeolitic, Licence: CC BY 4.0
Life restoration of the Mongolian alvarezsaurid Mononykus olecranus.
Therizinosaurus Restoration.png
Author/Creator: PaleoNeolitic, Licence: CC BY 4.0
Life restoration of the gigantic, Late Cretaceous therizinosaurid Therizinosaurus cheloniformis. Claws and arms based on holotype PIN 551-483 and specimens IGM 100/15, 100/16 and 100/17.
Cruralispennia reconstruction.tif
Author/Creator: Fanboyphilosopher (Neil Pezzoni), Licence: CC BY-SA 4.0
A life reconstruction of the enantiornithean Cruralispennia multidonta.
Utahraptor Restoration.png
Author/Creator: Fred Wierum, Licence: CC BY-SA 4.0
Artistic restoration of Utahraptor ostrommaysorum
Confuciusornis plumage pattern.jpg
Author/Creator: Art by Velizar Simeonovski. Published by Quanguo Li​, Julia A. Clarke, Ke-Qin Gao, Jennifer A. Peteya, Matthew D. Shawkey, Licence: CC BY 4.0

Reconstruction of the plumage in Confuciusornis CUGB P140.

Morphological data and probable eumelanin signatures are consistent darker preserved regions as associated with dark colors in the fossil (sampling regime explained in Fig. 1).
Austroraptor Restoration.png
Author/Creator: Fred Wierum, Licence: CC BY-SA 4.0
Artistic restoration of Austroraptor cabazai
Complete Tyrannosaurus rex skull, AMNH 5027.
Ambopteryx restoration.png
Author/Creator: Audrey.m.horn, Licence: CC BY-SA 4.0
Restoration of Ambopteryx longibrachium based on known fossil elements
Anchiornis martyniuk.png
Author/Creator: Matt Martyniuk, Licence: CC BY 3.0
Illustration of the basal troodontid Anchiornis huxleyi, by Matt Martyniuk. Digital. Colors based on the patterns recovered by Li et al. 2010.
Patagopteryx deferrariisi.jpg
Author/Creator: FunkMonk (Michael B. H.), Licence: CC BY-SA 3.0
Patagopteryx deferrariisi
Apatoraptor NT small.jpg
Author/Creator: Nobu Tamura email:nobu.tamura@yahoo.com http://spinops.blogspot.com/ http://paleoexhibit.blogspot.com/, Licence: CC BY-SA 4.0
Apatoraptor pennatus
Confuciusornis sanctus mmartyniuk.png
Author/Creator: Matt Martyniuk, Licence: CC BY-SA 3.0
Restoration of the Mesozoic avialan Confuciusornis sanctus (long tailed/male? specimen) in mid-glide. Illustration by Matt Martyniuk, attribution required (see license).
Archaeopteryx lithographica - Pedro José Salas Fontelles (flipped).jpg
Author/Creator: Pedro José Salas Fontelles, Licence: CC BY-SA 3.0
Restauración del aspecto en vida del dinosaurio transicional Archaeopteryx lithographica que habitó en el Jurásico tardío, hace unos 150 millones de años, en lo que hoy es el sur de Alemania. Está realizado a partir del esqueletal realizado por el paleontólogo Scott Hartman.


Éste fósil tiene una importancia vital en el estudio de las aves y su evolución a partir de los dinosaurios, así como la aparición del vuelo en estos animales.

La ilustración representa la coloración que se le atribuye a Archaeopteryx gracias al estudio de los melanosomas. Se sabe que predominaba una coloración oscura o negruzca en todo el animal con las puntas de las plumas de vuelo de color más oscuro que el resto del cuerpo. Me he inspirado en el plumaje del Cormorán grande Phalacrocorax carbo.
Longipteryx restoration.jpg
Author/Creator: El fosilmaníaco, Licence: CC BY-SA 4.0
Life restoration of Longipteryx chaoyangensis, an enantiornithine bird which lived in China during the Early Cretaceous period, around 120 million years ago
Jeholornis mmartyniuk wiki (fipped).jpg
Author/Creator: Matt Martyniuk, Licence: CC BY-SA 3.0
Illustration of the basal avialan bird Shenzhouraptor sinensis (aka Jeholornis prima) by Matt Martyniuk. Graphite and digital. Based upon skeletal reconstructions by Scott Hartman and figures provided in: Zhou, Z.-H., and Zhang, F.-C. (2003). "Jeholornis compared to Archaeopteryx, with a new understanding of the earliest avian evolution." Naturwissenschaften, 90(5): 220-225.
Author/Creator: GabrielNU, Licence: CC BY-SA 4.0
Reconstruction of Patagonykus puertai. Based on Novas (1997); missing portions follow typical alvarezsaurid proportions (e.g. Shuvuuia)
(c) FunkMonk, CC BY 3.0
Zanabazar junior (formerly Saurornithoides).
Microraptor Restoration (cropped).png
Author/Creator: Fred Wierum, Licence: CC BY-SA 4.0
Microraptor gui reconstruction cropped for use in navboxes, etc.
Jeholornis prima NMNS.jpg
Author/Creator: Tiouraren (Y.-C. Tsai), Licence: CC BY-SA 4.0
Fossil specimen of Jeholornis prima, collected from Chaoyang, Liaoning, China. The specimen (BMNHC Ph780) is a collection of Beijing Museum of Natural History and was on display in the National Museum of Natural Science (Taichung, Taiwan) during a special exhibition.