Pelvis morphology suggests that early Mesozoic birds were too heavy to contact incubate their eggs

Journal of Evolutionary Biology
D Charles Deeming, Gerald Mayr

Abstract

Numerous new fossils have driven an interest in reproduction of early birds, but direct evidence remains elusive. No Mesozoic avian eggs can be unambiguously assigned to a species, which hampers our understanding of the evolution of contact incubation, which is a defining feature of extant birds. Compared to living species, eggs of Mesozoic birds are relatively small, but whether the eggs of Mesozoic birds could actually have borne the weight of a breeding adult has not yet been investigated. We estimated maximal egg breadth for a range of Mesozoic avian taxa from the width of the pelvic canal defined by the pubic symphysis. Known elongation ratios of Mesozoic bird eggs allowed us to predict egg mass and hence the load mass an egg could endure before cracking. These values were compared to the predicted body masses of the adult birds based on skeletal remains. Based on 21 fossil species, we show that for nonornithothoracine birds body mass was 187% of the load mass of the eggs. For Enantiornithes, body mass was 127% greater than the egg load mass, but some early Cretaceous ornithuromorphs were 179% heavier than their eggs could support. Our indirect approach provides the best evidence yet that early birds could not have sat on ...Continue Reading

References

Oct 23, 2004·Science·Zhonghe Zhou, Fucheng Zhang
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Sep 2, 2010·Proceedings of the National Academy of Sciences of the United States of America·Leon HuynenDavid M Lambert
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May 17, 2013·Biology Letters·Geoffrey F BirchardD Charles Deeming
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Jun 13, 2015·Royal Society Open Science·D Charles Deeming, Marcello Ruta
Jul 16, 2015·PloS One·Vincent FernandezMartin Kundrát
Oct 29, 2017·Scientific Reports·Jia-Yang JuangHsin-I Hsieh

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Citations

May 16, 2018·Journal of Experimental Zoology. Part A, Ecological and Integrative Physiology·D Charles Deeming
Apr 30, 2021·Evolution; International Journal of Organic Evolution·Lucas J Legendre, Julia A Clarke

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