Mesozoic Birds

Abstract

Birds are living dinosaurs, an evolutionary transition increasingly well documented in the abundant fossil record of Mesozoic birds. The avian fossil record begins 150 Ma (million years ago) in the late Jurassic, and for the next 85 million years, birds experienced an evolutionary radiation resulting in a wide range of body forms and lifestyles, occupying all continents and many different environments. This Mesozoic radiation culminated in the appearance of modern birds, Neornithes, in the late Cretaceous, and the loss of several archaic groups during the mass extinction event at the end of this period.

Key Concepts

  • Birds evolved from maniraptoran theropod dinosaurs during the middle of the Mesozoic Era, over 150 Ma (million years ago).
  • Many unique adaptations of modern birds, from flight feathers to coloured eggs, evolved amongst their dinosaurian predecessors.
  • A broad diversity of pre‐modern birds lived during the Cretaceous Period, their fossil record is well known from about 131 to 66 Ma.
  • The Mesozoic radiation of pre‐modern birds paralleled many aspects of the biology of their living counterparts.
  • Neornithes, or modern birds, originated in the late Cretaceous, were the only group of birds to survive the extinction event at the end of this period, and went on to diversify into the abundant forms seen today.

Keywords: Aves; evolution; palaeontology; flight; Mesozoic; dinosaurs

Figure 1. Evolutionary relationships of dinosaurs (including birds). A wide range of evidence supports the notion that birds (Archaeopteryx plus the groups leading to Neornithes or modern birds) are nested within the paravian dinosaurs – birds are a branch of the dinosaur family tree.
Figure 2. Selected examples of paravians including birds: (a) the dromaeosaurid Microraptor, (b) the late Jurassic Archaeopteryx, (c) the enantiornithine Protopteryx, (d) the ornithuromorph Gansus. Microraptor, Protopteryx and Gansus are from the famous early Cretaceous Jehol Biota of northeastern China. Scale bars equal 5 cm.
Figure 3. General trends towards the modernization (direction of arrow) of the foot, tail (orange‐brown circles) and hand (blue circles) of birds.
Figure 4. Evolutionary relationships of the main groups of Mesozoic birds (Aves). The black diamonds/rhombs indicate the known occurrence (in millions of years) of the different groups.
Figure 5. Selected examples of exceptional preservation among the early Cretaceous birds from the Jehol Biota (approximately 131–120 Ma ) of northeastern China: (a) close up of the primary feathers of Sapeornis, (b) foot scales and feathers of the ornithuromorph Yanornis, (c) and (d) forelimb of the ornithuromorph Hongshanornis showing skin folds (whitish integument in (d)) characteristic of modern birds, (e) toe pads of Sapeornis; (f) crop containing grains (white arrow) in Sapeornis, (g) gastroliths (or ‘gizzard stones’) in the ornithuromorph Gansus, (h) a feathered enantiornithine hatchling, (i) structures interpreted as ovarian follicles (white arrow) in an ornithuromorph (a controversial interpretation). Scale bars equal 1 cm.
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Further Reading

Chiappe LM and Witmer LM (eds) (2002) Mesozoic Birds: Above the Heads of Dinosaurs. Berkeley: California, USA.

Chiappe LM (2007) Glorified DinosaursGlorified Dinosaurs: The Origin and Early Evolution of Birds. John Wiley & Sons, Inc.: Hoboken, New Jersey, USA.

Chiappe LM and Qingjin M (2016) Birds of Stone: Chinese Avian Fossils from the Age of Dinosaurs. Johns Hopkins University Press: Baltimore.

Mayr G (2016) Avian Evolution: the Fossil Record of Birds and its Paleobiological Significance. Hoboken: New Jersey, USA.

O'Connor J and Zhou Z (2015) Early evolution of the biological bird: perspectives from new fossil discoveries in China. Journal of Ornithology 156 (1): 333–342.

Padian K and Chiappe LM (1998) The origin and early evolution of birds. Biological Reviews 73 (1): 1–42.

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How to Cite close
Chiappe, Luis M, and Bell, Alyssa(Oct 2020) Mesozoic Birds. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0029218]