Avemetatarsalia

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Avemetatarsalians
Temporal range:
Middle Triassic – Present, 247–0  Ma
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(possible Early Triassic record if Prorotodactylus is part of the clade [1] )
Avemetatarsalia Infobox Panoply.png
Seven avemetatarsalians (top left to bottom right): a Gentoo penguin, Marasuchus , Kentrosaurus , Thalassodromeus (foreground) with Anhanguera (background), Diplodocus , Rhamphorhynchus
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Sauropsida
Clade: Archosauria
Clade: Avemetatarsalia
Benton, 1999
Subgroups
Synonyms
  • Dracones Haeckel, 1895
  • Ornithosuchia Huene, 1908
  • OrnithotarsiGauthier, 1986
  • Pan-AvesGauthier and de Queiroz, 2001

Avemetatarsalia (meaning "bird metatarsals") is a clade of diapsid reptiles containing all archosaurs more closely related to birds than to crocodilians. [2] The two most successful groups of avemetatarsalians were the dinosaurs and pterosaurs. Dinosaurs were the largest terrestrial animals for much of the Mesozoic Era, and one group of small feathered dinosaurs (Aves, i.e. birds) has survived up to the present day. Pterosaurs were the first flying vertebrates and persisted through the Mesozoic before dying out at the Cretaceous-Paleogene (K-Pg) extinction event. Both dinosaurs and pterosaurs appeared in the Triassic Period, shortly after avemetatarsalians as a whole. [2] [3] The name Avemetatarsalia was first established by British palaeontologist Michael Benton in 1999. An alternate name is Pan-Aves, or "all birds", in reference to its definition containing all animals, living or extinct, which are more closely related to birds than to crocodilians. [4]

Contents

Although dinosaurs and pterosaurs were the only avemetatarsalians to survive past the end of the Triassic, other groups flourished during the Triassic. The most basal (earliest-branching) and plesiomorphic ("primitive") known avemetatarsalians were the aphanosaurs. Aphanosaurs were rare, four-legged carnivores which were only properly distinguished as a group in 2017. [5] The split between dinosaurs and pterosaurs occurred just after aphanosaurs branched off the archosaur family tree. This split corresponds to the subgroup Ornithodira (Ancient Greek ὄρνις (órnis, “bird”) + δειρή (deirḗ, “throat”), defined as the last common ancestor of dinosaurs and pterosaurs, and all of its descendants. Until the discovery of aphanosaurs, Ornithodira and Avemetatarsalia were considered roughly equivalent concepts. [3]

Pterosauromorpha includes all avemetatarsalians closer to pterosaurs than to dinosaurs. True non-pterosaur pterosauromorphs have been historically difficult to determine. Small, insectivorous archosaurs of the family Lagerpetidae may potentially be examples, alongside the similar genus Scleromochlus . [6] Dinosauromorpha, on the other hand, includes all avemetatarsalians closer to dinosaurs than to pterosaurs. Probable non-dinosaur dinosauromorphs include the diverse and widespread silesaurids, as well as more controversial and fragmentary taxa such as Marasuchus , Lagosuchus , Nyasasaurus , and Saltopus . Lagerpetids were also traditionally considered dinosauromorphs, [7] [3] though this has been more recently debated. [8] [6] [9]

Description

The "advanced mesotarsal" ankle present in most avemetatarsalians. AdvMesotarsal.png
The "advanced mesotarsal" ankle present in most avemetatarsalians.

The foundational characteristic is the "advanced mesotarsal" ankles, which are characterized by a large astragalus and a small calcaneum. This ankle orientation operated on a single hinge, allowing for better mobility. Probably as a result of this change, the common ancestor of the avemetatarsalians had an upright, bipedal posture, with their legs extending vertically, similar to that of mammals.

Feathers and other filamentary structures are known across the avemetatarsalians, from the downy pycnofibers of pterosaurs, to quill-like structures present in ornithischian dinosaurs, such as Psittacosaurus and Tianyulong , to feathers in theropod dinosaurs and their descendants, birds.

Two clades of avemetatarsalians, pterosaurs and birds, independently evolved flight. Pterosaurs are the earliest vertebrates known to have evolved powered flight. Their wings are formed by a membrane of skin, muscle, and other tissues stretching from the ankles to a dramatically lengthened fourth finger. [10] Birds evolved flight much later. Their wings formed from elongated fingers and their arms, all covered with flight feathers.

Avemetatarsalians were generally more lightly built than crocodile-line archosaurs. They had smaller heads and usually a complete lack of osteoderms.

Origin

Bird-line archosaurs appear in the fossil record by the Anisian stage of the Middle Triassic about 245 million years ago, represented by the dinosauriform Asilisaurus . However, Early Triassic fossil footprints reported in 2010 from the Świętokrzyskie (Holy Cross) Mountains of Poland may belong to a more primitive dinosauromorph. [1] If so, the origin of avemetatarsalians would be pushed back into the early Olenekian age, around 249 Ma. The oldest Polish footprints are classified in the ichnogenus Prorotodactylus and were made by an unknown small quadrupedal animal, but footprints called Sphingopus , found from Early Anisian strata, show that moderately large bipedal dinosauromorphs had appeared by 246 Ma. The tracks show that the dinosaur lineage appeared soon after the Permian–Triassic extinction event. Their age suggests that the rise of dinosaurs was slow and drawn out across much of the Triassic. [1] The primitive traits found in the quadrupedal aphanosaur Teleocrater shows that the earliest avemetatarsalians had many pseudosuchian-like features, and that the traits typical for the group evolved later. [11]

Classification

In 1986, Jacques Gauthier defined the name Ornithosuchia (previously coined by Huene) for a branch-based clade including all archosaurs more closely related to birds than to crocodiles. [7] In the same year, Gauthier also coined and defined a slightly more restrictive node-based clade, Ornithodira, containing the last common ancestor of the dinosaurs and the pterosaurs and all of its descendants. Paul Sereno in 1991 gave a different definition of Ornithodira, one in which Scleromochlus was explicitly added. [12] It was thus a potentially larger group than the Ornithodira of Gauthier. In 1999 Michael Benton concluded that Scleromochlus was indeed outside Gauthier's original conception of Ornithodira, so he named a new branch-based clade for this purpose: Avemetatarsalia, named after the birds (Aves), the last surviving members of the clade, and the metatarsal ankle joint that was a typical character of the group. Avemetatarsalia was defined as all Avesuchia closer to Dinosauria than to Crocodylia. In 2005, Sereno stated the opinion that Ornithodira was not a useful concept, whereas Avemetatarsalia was. In 2001, the same clade was given the name "Panaves" (lit. 'all birds', from Greek pan- + Latin aves ), coined by Jacques Gauthier. He defined it as the largest and most inclusive clade of archosaurs containing Aves (birds, anchored on Vultur gryphus) but not Crocodylia (anchored on Crocodylus niloticus). Gauthier referred Aves, all other Dinosauria, all Pterosauria, and a variety of Triassic archosaurs, including Lagosuchus and Scleromochlus, to this group. [13]

In a 2005 review of archosaur classification, Phil Senter attempted to resolve this conflicting set of terminology by applying strict priority to names based on when and how they were first defined. [14] Senter noted that Ornithosuchia, the earliest name used for the total group of archosaurs closer to birds than to crocodiles, should be the valid name for that group, and have precedence over later names with identical definitions, such as Avemetatarsalia and Pan-Aves. While this has been followed by some researchers, others have either continued to use Avemetatarsalia or Ornithodira, or have followed Senter only reluctantly. Mike Taylor (2007) for example noted that, while Senter is correct in stating that Ornithosuchia has priority, this is "undesirable" because it probably excludes the eponymous family Ornithosuchidae, and questioned the utility of using priority before the PhyloCode is implemented to govern it. [15] In fact, the name Ornithosuchia may be "illegal" under the PhyloCode because it does not include its eponymous taxon as part of its definition. [15]

Cladogram after Nesbitt et al. (2017), [16] with clade names from Cau (2018). [17]

Archosauria

Pseudosuchia (crocodile-line archosaurs) Deinosuchus riograndensis.png

Avemetatarsalia

Kammerer et al. (2020) and Ezcurra et al. (2020) supported an alternative hypothesis regarding the relationships of lagerpetids. They were interpreted as non-pterosaur pterosauromorphs. This phylogeny would shorten the morphological and chronological gap perceived between pterosaurs and other stem-birds, and explain the origin of this group. [8] [6] Bennett (2020) argued that Scleromochlus, a genus historically considered a relative of ornithodirans or even a basal pterosauromorph, was instead a non-archosaur archosauriform (possibly a doswelliid). [18]

In 2023, Nesbitt et al. described Mambachiton as the earliest diverging avemetatarsalian, outside of the minimally inclusive clade containing aphanosaurs and ornithodirans. Preliminary analyses had considered Mambachiton to be a basal poposauroid (a clade of pseudosuchians), though the later recognition of aphanosaurs as basal avemetatarsalians corrected this view. The results of the phylogenetic analyses of Nesbit et al. (2023) are shown in the cladogram below: [19]

Archosauria

Related Research Articles

<span class="mw-page-title-main">Archosaur</span> Group of diapsids broadly classified as reptiles

Archosauria or archosaurs is a clade of diapsid sauropsid tetrapods, with birds and crocodilians being the only extant representatives. Although broadly classified as reptiles, which traditionally exclude birds, the cladistic sense of the term includes all living and extinct relatives of birds and crocodilians such as non-avian dinosaurs, pterosaurs, phytosaurs, aetosaurs and rauisuchians as well as many Mesozoic marine reptiles. Modern paleontologists define Archosauria as a crown group that includes the most recent common ancestor of living birds and crocodilians, and all of its descendants.

<span class="mw-page-title-main">Archosauriformes</span> Clade of reptiles

Archosauriformes is a clade of diapsid reptiles encompassing archosaurs and some of their close relatives. It was defined by Jacques Gauthier (1994) as the clade stemming from the last common ancestor of Proterosuchidae and Archosauria. Phil Senter (2005) defined it as the most exclusive clade containing Proterosuchus and Archosauria. Archosauriforms are a branch of archosauromorphs which originated in the Late Permian and persist to the present day as the two surviving archosaur groups: crocodilians and birds.

<i>Scleromochlus</i> Extinct genus of reptiles

Scleromochlus is an extinct genus of small pterosauromorph archosaurs from the Late Triassic Lossiemouth Sandstone of Scotland. The genus contains the type and only species Scleromochlus taylori, named by Arthur Smith Woodward in 1907.

Spondylosoma is a genus of avemetatarsalian archosaur belonging to the clade Aphanosauria from the late Ladinian-age Middle Triassic Lower Santa Maria Formation in Paleorrota Geopark, Brazil.

<i>Lagerpeton</i> Extinct genus of reptiles

Lagerpeton is a genus of lagerpetid avemetatarsalian, comprising a single species, L. chanarensis. First described from the Chañares Formation of Argentina by A. S. Romer in 1971, Lagerpeton's anatomy is somewhat incompletely known, with fossil specimens accounting for the pelvic girdle, hindlimbs, posterior presacral, sacral and anterior caudal vertebrae. Skull and shoulder material has also been described.

<span class="mw-page-title-main">Pseudosuchia</span> Clade of reptiles

Pseudosuchia is one of two major divisions of Archosauria, including living crocodilians and all archosaurs more closely related to crocodilians than to birds. Pseudosuchians are also informally known as "crocodilian-line archosaurs". Despite Pseudosuchia meaning "false crocodiles", the name is a misnomer as true crocodilians are now defined as a subset of the group.

<i>Nyasasaurus</i> Extinct genus of reptiles

Nyasasaurus is an extinct genus of avemetatarsalian archosaur from the putatively Middle Triassic Manda Formation of Tanzania that may be the earliest known dinosaur. The type species Nyasasaurus parringtoni was first described in 1956 in the doctoral thesis of English paleontologist Alan J. Charig, but it was not formally described until 2013.

<i>Teleocrater</i> Extinct genus of reptiles

Teleocrater is a genus of avemetatarsalian archosaur from the Middle Triassic Manda Formation of Tanzania. The name was coined by English paleontologist Alan Charig in his 1956 doctoral dissertation, but was only formally published in 2017 by Sterling Nesbitt and colleagues. The genus contains the type and only species T. rhadinus. Uncertainty over the affinities of Teleocrater have persisted since Charig's initial publication; they were not resolved until Nesbitt et al. performed a phylogenetic analysis. They found that Teleocrater is most closely related to the similarly enigmatic Yarasuchus, Dongusuchus, and Spondylosoma in a group that was named the Aphanosauria. Aphanosauria was found to be the sister group of the Ornithodira, the group containing dinosaurs and pterosaurs.

<span class="mw-page-title-main">Dinosauromorpha</span> Clade of reptiles

Dinosauromorpha is a clade of avemetatarsalians that includes the Dinosauria (dinosaurs) and some of their close relatives. It was originally defined to include dinosauriforms and lagerpetids, with later formulations specifically excluding pterosaurs from the group. Birds are the only dinosauromorphs which survive to the present day.

<span class="mw-page-title-main">Pterosauromorpha</span> Extinct clade of reptiles

Pterosauromorpha is one of the two basic divisions of Ornithodira that includes pterosaurs and all taxa that are closer to them than to dinosaurs and their close relatives. In addition to pterosaurs, Pterosauromorpha also includes the basal clade Lagerpetidae and some other Late Triassic ornithodirans.

<i>Yarasuchus</i> Extinct genus of reptiles

Yarasuchus is an extinct genus of avemetatarsalian archosaur that lived during the Anisian stage of the Middle Triassic of India. The genus was named and described in 2005 from a collection of disarticulated but fairly complete fossil material found from the Middle Triassic Yerrapalli Formation. The material is thought to be from two individuals, possibly three, with one being much more complete and articulated than the other. The type and only species is Y. deccanensis. Yarasuchus was a quadruped roughly 2–2.5 metres (6.6–8.2 ft) long, with an elongated neck and tall spines on its vertebrae. Unlike other quadrupedal Triassic reptiles, the limbs and shoulders of Yarasuchus were slender, and more like those of ornithodirans.

Sterling Nesbitt is an American paleontologist best known for his work on the origin and early evolutionary patterns of archosaurs. He is currently an associate professor at Virginia Tech in the Department of Geosciences.

<span class="mw-page-title-main">Silesauridae</span> Extinct family of dinosaur-like reptiles

Silesauridae is an extinct family of Triassic dinosauriforms. It is most commonly considered to be a clade of non-dinosaur dinosauriforms, and the sister group of dinosaurs. Some studies have instead suggested that most or all silesaurids comprised an early diverging clade or a paraphyletic grade within ornithischian dinosaurs. Silesaurids have a consistent general body plan, with a fairly long neck and legs and possibly quadrupedal habits, but most silesaurids are heavily fragmentary nonetheless. Furthermore, they occupied a variety of ecological niches, with early silesaurids being carnivorous and later taxa having adaptations for specialized herbivory. As indicated by the contents of referred coprolites, Silesaurus may have been insectivorous, feeding selectively on small beetles and other arthropods.

<span class="mw-page-title-main">Lagerpetidae</span> Extinct family of reptiles

Lagerpetidae is a family of basal avemetatarsalians. Though traditionally considered the earliest-diverging dinosauromorphs, fossils described in 2020 suggest that lagerpetids may instead be pterosauromorphs. Lagerpetid fossils are known from the Triassic of Argentina, Arizona, Brazil, Madagascar, New Mexico, and Texas. They were typically small, although some lagerpetids, like Dromomeron gigas and a specimen from the Santa Rosa Formation attributed to Dromomeron sp., were able to get quite large. Lagerpetid fossils are rare; the most common finds are bones of the hindlimbs, which possessed a number of unique features.

Faxinalipterus is a genus of ornithodiran archosaur, originally described as a pterosaur, from the Late Triassic Caturrita Formation of southern Brazil. A study from 2022 reinterpreted the fossil remains and instead suggests them to belong to a member of the Lagerpetidae, another clade of pterosauromorphs.

<i>Diodorus scytobrachion</i> Extinct species of reptile

Diodorus is a genus of silesaurid dinosauromorph that lived during the Late Triassic in what is now Morocco. Fossils were discovered in the Timezgadiouine Formation of the Argana Basin, and were used to name the new genus and species Diodorus scytobrachion. The genus name honors the mythological king Diodorus and the ancient historian Diodorus Siculus; the specific name is ancient Greek for 'leathery arm' and also honors the mythographer Dionysius Scytobrachion. The holotype specimen is a partial dentary bone (front of the lower jaw), and assigned specimens include isolated teeth, two humeri (upper arm bones), a metatarsal (foot bone), and femur (thigh bone).

Aphanosauria is an extinct group of reptiles distantly related to dinosaurs. They are at the base of a group known as Avemetatarsalia, one of two main branches of archosaurs. The other main branch, Pseudosuchia, includes modern crocodilians. Aphanosaurs possessed features from both groups, indicating that they are the oldest and most primitive known clade of avemetatarsalians, at least in terms of their position on the archosaur family tree. Other avemetatarsalians include the flying pterosaurs, small bipedal lagerpetids, herbivorous silesaurids, and the incredibly diverse dinosaurs, which survive to the present day in the form of birds. Aphanosauria is formally defined as the most inclusive clade containing Teleocrater rhadinus and Yarasuchus deccanensis but not Passer domesticus or Crocodylus niloticus. This group was first recognized during the description of Teleocrater. Although only known by a few genera, Aphanosaurs had a widespread distribution across Pangaea in the Middle Triassic. They were fairly slow quadrupedal long-necked carnivores, a biology more similar to basal archosaurs than to advanced avemetatarsalians such as pterosaurs, lagerpetids, and early dinosaurs. In addition, they seemingly possess 'crocodile-normal' ankles, showing that 'advanced mesotarsal' ankles were not basal to the whole clade of Avemetatarsalia. Nevertheless, they possessed elevated growth rates compared to their contemporaries, indicating that they grew quickly, more like birds than other modern reptiles. Despite superficially resembling lizards, the closest modern relatives of aphanosaurs are birds.

<i>Kongonaphon</i> Extinct genus of reptiles

Kongonaphon is an extinct genus of lagerpetid avemetatarsalians from the Middle to Late Triassic of Madagascar. It contains a single species, Kongonaphon kely, which is known from a fragmentary partial skeleton. This fossil hails from the late Ladinian or early Carnian-age "basal Isalo II beds". As the first lagerpetid found in Africa, Kongonaphon extends the range of the family significantly. It possessed a combination of features from various other lagerpetids, but developed particularly long and slender leg bones. Kongonaphon is also the first lagerpetid for which fossils of the snout and teeth are known. It was likely an insectivore based on the shape and texture of its teeth.

<i>Maehary</i> Extinct genus of pseudosuchian archosaurs

Maehary is an extinct genus of probable gracilisuchid pseudosuchian archosaurs from the Late Triassic (Norian) Caturrita Formation of Rio Grande do Sul, Brazil. The genus contains a single species, M. bonapartei, known from a partial skull and fragmentary postcrania. Maehary was originally described as the basalmost member of the Pterosauromorpha, but several subsequent studies have suggested pseudosuchian affinities are more likely. If this is correct, it would represent the youngest known member of the Gracilisuchidae.

Mambachiton is an extinct genus of basal avemetatarsalian from the Middle/Upper Triassic Makay Formation of Madagascar. The genus contains a single species, M. fiandohana, known from a partial skeleton with articulated osteoderms.

References

  1. 1 2 3 Brusatte, S. L.; Niedźwiedzki, G.; Butler, R. J. (2011). "Footprints pull origin and diversification of dinosaur stem lineage deep into Early Triassic". Proceedings of the Royal Society B: Biological Sciences. 278 (1708): 1107–1113. doi:10.1098/rspb.2010.1746. PMC   3049033 . PMID   20926435.
  2. 1 2 Benton, M.J. (1999). "Scleromochlus taylori and the origin of dinosaurs and pterosaurs". Philosophical Transactions of the Royal Society B: Biological Sciences. 354 (1388): 1423–1446. doi:10.1098/rstb.1999.0489. PMC   1692658 .
  3. 1 2 3 Nesbitt, S.J. (2011). "The early evolution of archosaurs: relationships and the origin of major clades". Bulletin of the American Museum of Natural History. 352: 1–292. doi: 10.1206/352.1 . hdl:2246/6112. S2CID   83493714.
  4. ↑ Ezcurra, Martín D.; Nesbitt, Sterling J.; Bronzati, Mario; Dalla Vecchia, Fabio Marco; Agnolin, Federico L.; Benson, Roger B. J.; Brissón Egli, Federico; Cabreira, Sergio F.; Evers, Serjoscha W.; Gentil, Adriel R.; Irmis, Randall B.; Martinelli, Agustín G.; Novas, Fernando E.; Roberto da Silva, Lúcio; Smith, Nathan D.; Stocker, Michelle R.; Turner, Alan H.; Langer, Max C. (2020). "Enigmatic dinosaur precursors bridge the gap to the origin of Pterosauria". Nature. 588 (7838): 445–449. doi:10.1038/s41586-020-3011-4. ISSN   1476-4687. PMID   33299179. S2CID   228077525.
  5. ↑ Nesbitt, Sterling J.; Butler, Richard J.; Ezcurra, Martín D.; Barrett, Paul M.; Stocker, Michelle R.; Angielczyk, Kenneth D.; Smith, Roger M. H.; Sidor, Christian A.; Niedźwiedzki, Grzegorz; Sennikov, Andrey G.; Charig, Alan J. (2017). "The earliest bird-line archosaurs and the assembly of the dinosaur body plan" (PDF). Nature. 544 (7651): 484–487. Bibcode:2017Natur.544..484N. doi:10.1038/nature22037. PMID   28405026. S2CID   9095072.
  6. 1 2 3 Ezcurra, Martín D.; Nesbitt, Sterling J.; Bronzati, Mario; Dalla Vecchia, Fabio Marco; Agnolin, Federico L.; Benson, Roger B. J.; Brissón Egli, Federico; Cabreira, Sergio F.; Evers, Serjoscha W.; Gentil, Adriel R.; Irmis, Randall B. (2020-12-17). "Enigmatic dinosaur precursors bridge the gap to the origin of Pterosauria". Nature. 588 (7838): 445–449. doi:10.1038/s41586-020-3011-4. ISSN   0028-0836. PMID   33299179. S2CID   228077525.
  7. 1 2 Gauthier, Jacques (1986). "Saurischian monophyly and the origin of birds". In Padian, Kevin (ed.). The Origin of Birds and the Evolution of Flight. Memoirs of the California Academy of Sciences. Vol. 8. San Francisco: California Academy of Sciences. pp. 1–55.
  8. 1 2 Kammerer, Christian F.; Nesbitt, Sterling J.; Flynn, John J.; Ranivoharimanana, Lovasoa; Wyss, André R. (2020-07-28). "A tiny ornithodiran archosaur from the Triassic of Madagascar and the role of miniaturization in dinosaur and pterosaur ancestry". Proceedings of the National Academy of Sciences. 117 (30): 17932–17936. doi: 10.1073/pnas.1916631117 . ISSN   0027-8424. PMC   7395432 . PMID   32631980.
  9. ↑ Baron, Matthew G. (2021-08-20). "The origin of Pterosaurs". Earth-Science Reviews. 221: 103777. doi:10.1016/j.earscirev.2021.103777. ISSN   0012-8252.
  10. ↑ Elgin RA, Hone DW, Frey E (2011). "The Extent of the Pterosaur Flight Membrane". Acta Palaeontologica Polonica. 56 (1): 99–111. doi: 10.4202/app.2009.0145 .
  11. ↑ Dinosaur Evolution: Crocodile-Like Ancient Cousin, Teleocrater Rhadinus, Confuses Scientists
  12. ↑ Sereno, P. C. 1991. Basal archosaurs: phylogenetic relationships and functional implications. Journal of Vertebrate PaleontologyMemoir 2, 11(4, Supplement):1–53.
  13. ↑ Gauthier, J. and de Queiroz, K. (2001). "Feathered dinosaurs, flying dinosaurs, crown dinosaurs, and the name "Aves"". pp. 7–41 in Gauthier, J. and L. F. Gall (eds.), New Perspectives on the Origin and Early Evolution of Birds: Proceedings of the International Symposium in Honor of John H. Ostrom. New Haven: Peabody Museum of Natural History, Yale University. ISBN   0-912532-57-2.
  14. ↑ Senter, P. (2005). "Phylogenetic taxonomy and the names of the major archosaurian (Reptilia) clades". PaleoBios. 25 (3): 1–7.
  15. 1 2 Taylor (2007). "Phylogenetic definitions in the pre-PhyloCode era; implications for naming clades under the PhyloCode" (PDF). PaleoBios. 27 (1): 1–6.
  16. ↑ Nesbitt, Sterling J.; Butler, Richard J.; Ezcurra, Martín D.; Barrett, Paul M.; Stocker, Michelle R.; Angielczyk, Kenneth D.; Smith, Roger M. H.; Sidor, Christian A.; Niedźwiedzki, Grzegorz; Sennikov, Andrey G.; Charig, Alan J. (2017). "The earliest bird-line archosaurs and the assembly of the dinosaur body plan" (PDF). Nature. 544 (7651): 484–487. doi:10.1038/nature22037. PMID   28405026. S2CID   9095072.
  17. ↑ Andrea Cau (2018). "The assembly of the avian body plan: a 160-million-year long process" (PDF). Bollettino della Società Paleontologica Italiana. 57 (1): 1–25. doi:10.4435/BSPI.2018.01.
  18. ↑ Bennett, S. Christopher (2020-02-19). "Reassessment of the Triassic archosauriform Scleromochlus taylori: neither runner nor biped, but hopper". PeerJ. 8: e8418. doi: 10.7717/peerj.8418 . ISSN   2167-8359. PMC   7035874 . PMID   32117608.
  19. ↑ Nesbitt, Sterling J.; Patellos, Emily; Kammerer, Christian F.; Ranivoharimanana, Lovasoa; Wyss, Andre´ R.; Flynn, John J. (2023-07-25). "The earliest-diverging avemetatarsalian: a new osteoderm-bearing taxon from the Triassic (?Earliest Late Triassic) of Madagascar and the composition of avemetatarsalian assemblages prior to the radiation of dinosaurs". Zoological Journal of the Linnean Society. 199 (2): 327–353. doi: 10.1093/zoolinnean/zlad038 . ISSN   0024-4082.

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