Why Were Extinct Gigantic Birds So Small?

  title={Why Were Extinct Gigantic Birds So Small?},
  author={D. Charles Deeming and Geoffrey F. Birchard},
  journal={Avian Biology Research},
  pages={187 - 194}
This review details the six lineages of large flightless birds that evolved in the Late Cretaceous, Tertiary and Quaternary periods of geological time. Estimates of mass for each type of bird suggest that maximal mass is no greater than 500kg with most species attaining only 250–300 kg or less. By contrast, non-avian Archosaurs of the Mesozoic, and many mammal species of the Tertiary, attained great size with many species reaching several tonnes. Size has been limited in flightless birds… Expand

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