Neornithes

Neornithes Gadow 1893[1] (=Aves sensu Gauthier 1986),[2] meaning "new birds"

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Neornithes are the most recent common ancestral species of all extant birds and all of said species' descendants. Neornithine anatomy has been reviewed most recently by Hope (2002),[3] who presented a succinct but precise account of the morphological changes associated with the derivation of crown clade birds. Synapomorphies (common features) of Neornithes include:

  1. Premaxilla/maxilla fused
  2. Maxilla greatly reduced and primarily restricted to the palatal region
  3. Mandibular symphysis fused
  4. Dentary and surangular fused
  5. Teeth absent
  6. Humeral facet of coracoid does not extend laterally beyond the scapular facet of the coracoid
  7. Scapular humeral facet is oriented laterally or craniolaterally
  8. Humeral facet of coracoid separated slightly or completely from the scapular facet
  9. Humeral head large
  10. Sulcus for transverse humeral ligament distinct
  11. Deltopectoral crest of humerus inflected cranially
  12. Pneumotricipital fossa pierced by a pneumatic foramen

The origin of Neornithes is one of the most contested issues in paleornithology, with two widely disparate models advanced to account for the evolution of this group (reviewed in Neornithine 'Big Bang'). Classically, Neornithes has been considered to cleave into two divergent lineages, the Paleognathae and the Neognathae, first delineated by Huxley on the basis of palatal configuration. Following the classification of Wetmore (1960),[4] Neornithes consists of the following orders:

Neornithes are divided into the following orders:

  • Tinamiformes
  • Casuariiformes
  • Struthioniformes
  • Rheiformes
  • Sphenisciformes
  • Gaviiformes
  • Podicipediformes
  • Procellariiformes
  • Pelecaniformes
  • Ciconiiformes
  • Anseriformes
  • Falconiformes
  • Galliformes
  • Gruiformes
  • Charadriiformes
  • Columbiformes
  • Psittaciformes
  • Cuculiformes
  • Strigiformes
  • Caprimulgiformes
  • Apodiformes
  • Coliiformes
  • Trogoniformes
  • Coraciiformes
  • Piciformes
  • Passeriformes

The constitution and phylogenetic placement of these taxa remains hotly contested in systematic ornithology, but some general conclusions can be made:

  • The ratite assemblage (Tinamiformes + Struthioniformes + Casuariiformes + Rheiformes) may be holophyletic.[5]
  • Charadriiform-like taxa (e.g., Graculavus) are the wellspring from which the principal neornithine adaptive radiation is derived.[6][7][8][9][10][11]
  • Ciconiiformes as classically defined is polyphyletic.[9]
  • Strigiformes and Caprimulgiformes are closely allied.[5]
  • Falconiformes as classically defined is polyphyletic.[5]
  • Gaviiformes and Podicipediformes are not closely related.[5][12]
  • Passeriformes is not a basal radiation within Neornithes.[13]

Further consensus is not readily possible and indeed even these conclusions presented here are contentious. Higher level systematics of the neornithine assemblage remain difficult to interpret despite a century of work on these birds, as noted by Streseman in the 1950s. Thus, neornithine evolution remains a fertile field for students of avian phylogeny.

References
  1. Gadow, H. 1893. Vogel II: Systematicher Theil. In: Bronn, H. G. (ed.), Klassen und Ordnungen dees Thier-Reichs, vol. 6(4). C. F.Winter, Leipzig.
  2. Gauthier, J. 1986. Saurischian monophyly and the origin of birds. Memoires of the California Academy of Sciences 8: 1-55.
  3. Hope, S. 2002. The Mesozoic radiation of Neornithes. In: Chiappe, L. & Witmer, L. (eds.), Mesozoic Birds: Above the Heads of Dinosaurs, 339-388.
  4. Wetmore, A. 1960. A classification for the birds of the world. Smithsonian Miscellaneous Collections 139: 1-37.
  5. Sibley, C. G. & Ahlquist, J. E. 1990. Phylogeny and Classification of Birds. Yale University Press, New Haven.
  6. Martin, L. D. 1983. The origin and early radiation of birds. In: Brush, A. H. & Clark, Jr., G. A. (eds.), Perspectives in Ornithology, 291-338.
  7. Olson, S. L. 1985. The fossil record of birds. In: Farner, D. S., King, J. R., and Parkes, K. C. (eds.), Avian Biology Volume VIII, 79-252.
  8. Feduccia, A. 1995. Explosive evolution in Tertiary birds and mammals. Science 267: 637-638.
  9. Feduccia, A. 1996. The Origin and Evolution of Birds, First Edition. Yale University Press, New Haven.
  10. Feduccia, A. 1999. The Origin and Evolution of Birds, Second Edition. Yale University Press, New Haven.
  11. Feduccia, A. 2003. 'Big bang' for Tertiary birds? Trends in Ecology and Evolution 18(4): 172-176.
  12. Storer, R. W. 1960. Evolution in the diving birds. Proceedings of the Twelfth International Ornithological Congress, 694-707.
  13. van Tuinen, M., Sibley, C. G., & Hedges, S. B. 2000. The early history of modern birds inferred from DNA sequences of nuclear and mitochondrial ribosomal genes. Molecular and Biological Evolution 17(3): 451-457.
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