Pterosauromorpha

Pterosauromorphs
Temporal range:
Late Triassic – Late Cretaceous, 236–66 Ma[1]
Skeletal restoration of Lagerpeton chanarensis (known elements represented in white)
Skeletal restoration of Dimorphodon macronyx
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Ornithodira
Clade: †Pterosauromorpha
Kuhn-Schnyder & Rieber, 1986
Subgroups

Pterosauromorpha (meaning "pterosaur-like forms") 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 (i.e. Dinosauromorpha).[2][3] In addition to pterosaurs, Pterosauromorpha also includes the basal clade Lagerpetidae and some other Late Triassic ornithodirans (Maehary and Scleromochlus).[4][5][6][7]

Classification

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Skeletal restoration of Scleromochlus

The name Pterosauromorpha was originally coined by Emil Kuhn-Schnyder and Hans Rieber (1986) for a reptilian subclass distinct from Archosauria which includes pterosaurs.[8] In 1997, Kevin Padian classified Pterosauromorpha as a clade of archosaurs and proposed phylogenetic definition for this group: "Pterosauria and all ornithodiran archosaurs closer to them than to dinosaurs".[2] Brian Andres and Kevin Padian redefined Pterosauromorpha as: "The clade consisting of Pterodactylus (originally Ornithocephalus) antiquus (Sömmerring 1812) (Pterosauria) and all organisms or species that share a more recent common ancestor with it than with Alligator (originally Crocodilus) mississippiensis (Daudin 1802) (Suchia) and Compsognathus longipes Wagner 1859 (Dinosauromorpha)".[3][9]

Lagerpetidae was traditionally considered the earliest diverging group of dinosauromorphs. This caused no other reptiles besides the true pterosaurs to be placed in Pterosauromorpha.[10][11] The only notable exception was a small reptile named Scleromochlus, whose placement within the clade itself remained controversial due the poor preservation of its otherwise complete remains. Different phylogenetic analyses found it as a basal pterosauromorph,[4][5] a non-aphanosaurian, non-pterosaur basal avemetatarsalian, a basal dinosauromorph,[11] or a basal archosauriform.[12] This has resulted in a large gap between the fully aerial pterosaurs and their terrestrial ancestors, as the earliest pterosaurs were already capable flyers.[11]

First iteration of phylogenetic analysis produced by Kammerer et al. (2020) restored lagerpetids as a basal dinosauromorphs, which corresponds to the traditional point of view. But the second iteration, in which were added Scleromochlus, found Lagerpetidae as the most basal pterosauromorphs, and Scleromochlus as the sister taxon of pterosaurs.[4] In a study that used micro-CT scans, Ezcurra et al. (2020) have found additional similarities, including large semicircular canals within the bones of some lagerpetids that resemble that of pterosaurs. It is assumed that large semicircular canals are related to arboreal, aerial or other agile forms of terrestrial locomotion as well as rapid movements. The flocculus, the part of the brain that aids in transmitting information, was also large in both pterosaurs and lagerpetids, though to a lesser extent. When Ezcurra et al. (2020) included Scleromochlus in their analysis, they found it to be the most basal pterosauromorph, sister to a clade including lagerpetids and pterosaurs.[5] Baron (2021) conducted his own analysis, which confirmed the relationship between lagerpetids and pterosaurs.[6]

It has to do with the semicircular canals [in the ear], which orients you in 3D space. The shape of those canals correlates with ecology and how you move your head — basically, are you agile or not? And a lot of things that have flight have semicircular canals with a really large and characteristic [shape] because you're flying, you're in a lot more 3D space.

— Sterling Nesbitt[13]

Kellner et al. (2022) described Maehary, a small ornithodiran from the Late Triassic of Brazil. It was interpreted as a basal pterosauromorph (along with lagerpetids). It is noteworthy that left maxilla of Maehary was previously considered to be a specimen of Faxinalipterus that was re-classified as a lagerpetid.[7]

References

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  1. ^ Claudia A. Marsicano; Randall B. Irmis; Adriana C. Mancuso; Roland Mundil; Farid Chemale (2016). "The precise temporal calibration of dinosaur origins". Proceedings of the National Academy of Sciences of the United States of America. 113 (3): 509–513. Bibcode:2016PNAS..113..509M. doi:10.1073/pnas.1512541112. PMC 4725541. PMID 26644579.
  2. ^ a b Padian, K. (1997). "Pterosauromorpha". In Currie, P. J.; Padian, K. (eds.). The Encyclopedia of Dinosaurs. Academic Press. pp. 617–618. ISBN 978-0-12-226810-6.
  3. ^ a b de Queiroz, K.; Cantino, P. D.; Gauthier, J. A., eds. (2020). "Pterosauromorpha E. Kuhn-Schnyder and H. Rieber 1986 [B. Andres and K. Padian], converted clade name". Phylonyms: A Companion to the PhyloCode. Boca Raton: CRC Press. pp. 1195–1199. ISBN 978-1-138-33293-5.
  4. ^ a b c Kammerer, C. F.; Nesbitt, S. J.; Flynn, J. J.; Ranivoharimanana, L.; Wyss, A. R. (2020). "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. Bibcode:2020PNAS..11717932K. doi:10.1073/pnas.1916631117. ISSN 0027-8424. PMC 7395432. PMID 32631980.
  5. ^ a b c d Ezcurra, M. D.; Nesbitt, S. J.; Bronzati, M.; Dalla Vecchia, F. M.; Agnolin, F. L.; Benson, R. B. J.; Brissón Egli, F.; Cabreira, S. F.; Evers, S. W.; Gentil, A. R.; et al. (2020). "Enigmatic dinosaur precursors bridge the gap to the origin of Pterosauria" (PDF). Nature. 588 (7838): 445–449. Bibcode:2020Natur.588..445E. doi:10.1038/s41586-020-3011-4. ISSN 0028-0836. PMID 33299179. S2CID 228077525.
  6. ^ a b Baron, M. G. (2021). "The origin of Pterosaurs". Earth-Science Reviews. 221: 103777. Bibcode:2021ESRv..22103777B. doi:10.1016/j.earscirev.2021.103777. ISSN 0012-8252.
  7. ^ a b c Kellner, A.W.A.; Holgado, B.; Grillo, O.; Pretto, F.A.; Kerber, L.; Pinheiro, F.L.; Soares, M.B.; Schultz, C.L.; Lopes, R.T.; Araújo, A.; Müller, R.T. (2022). "Reassessment of Faxinalipterus minimus, a purported Triassic pterosaur from southern Brazil with the description of a new taxon". PeerJ. 10: e13276. doi:10.7717/peerj.13276. PMC 9074864. PMID 35529502.
  8. ^ Kuhn-Schnyder, E.; Rieber, H. (1986). Handbook of Paleozoology. Baltimore, MD: Johns Hopkins University Press.
  9. ^ "Pterosauromorpha". RegNum. Retrieved 30 May 2022.
  10. ^ a b 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: 189. doi:10.1206/352.1. hdl:2246/6112. ISSN 0003-0090. S2CID 83493714.
  11. ^ a b c Nesbitt, S. J.; Butler, R. J.; Ezcurra, M. D.; Barrett, P. M.; Stocker, M. R.; Angielczyk, K. D.; Smith, R. M. H.; Sidor, C. A.; Niedźwiedzki, G.; Sennikov, A. G.; Charig, A. 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.
  12. ^ Bennett, S.C. (2020). "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.
  13. ^ ""Missing Link" in Pterosaurs' Family Tree Has Been Identified". Mysterious Universe. Jocelyne LeBlanc. December 16, 2020.
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