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Experimental Manipulation of Body Size to Estimate Morphological Scaling Relationships in Drosophila
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Published on: October 1, 2011

Body size evolution in Mesozoic birds.

D W E Hone1, G J Dyke, M Haden

  • 1Bayerische Staatssammlung für Paläontologie und Geologie, Richard-Wagner-Strasse, München, Germany. dhone@ivpp.ac.cn

Journal of Evolutionary Biology
|January 16, 2008
PubMed
Summary
This summary is machine-generated.

Contrary to expectations, flying birds evolved larger body sizes throughout the Jurassic and Cretaceous periods. This nonrandom increase in avian body size, driven by diversification, contrasts with the decrease seen in modern bird lineages.

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Area of Science:

  • Paleontology
  • Evolutionary Biology
  • Comparative Anatomy

Background:

  • Cope's Rule describes a general trend of increasing body size in evolving lineages.
  • Avian evolution presents a unique case due to flight constraints, suggesting potential limitations on body size increase.
  • Previous interpretations of early avian evolution have not consistently supported size increase.

Purpose of the Study:

  • To investigate body size trends in Jurassic and Cretaceous flying birds.
  • To determine if avian evolution followed Cope's Rule despite flight constraints.
  • To analyze body size changes within specific avian clades.

Main Methods:

  • Analysis of body size data from fossil flying birds across the Jurassic and Cretaceous periods.
  • Statistical examination of body size trends over a 70-million-year timespan.
  • Comparative analysis of body size changes within major avian clades (Pygostylia, Ornithothoraces, Ornithuromorpha).

Main Results:

  • Demonstrated an overall increase in body size across flying birds from the Early Jurassic to the end of the Cretaceous.
  • Identified a nonrandom, though not strictly directional, increase in avian body size over 70 million years.
  • Observed body size increase within Pygostylia and Ornithothoraces, but a decrease in the crownward lineage Ornithuromorpha (ancestral to extant birds).

Conclusions:

  • Avian evolution, contrary to some expectations, exhibited an overall increase in body size during the Mesozoic Era.
  • Diversification after the origin of flight likely facilitated this size increase, potentially through increased variance.
  • The decrease in body size in Ornithuromorpha may have contributed to their survival across the Cretaceous-Palaeogene boundary.