Dinosaur egg colour had a single evolutionary origin

@article{Wiemann2018DinosaurEC,
  title={Dinosaur egg colour had a single evolutionary origin},
  author={Jasmina Wiemann and Tzu-Ruei Yang and Mark A. Norell},
  journal={Nature},
  year={2018},
  volume={563},
  pages={555-558}
}
Birds are the only living amniotes with coloured eggs1–4, which have long been considered to be an avian innovation1,3. A recent study has demonstrated the presence of both red-brown protoporphyrin IX and blue-green biliverdin5—the pigments responsible for all the variation in avian egg colour—in fossilized eggshell of a nonavian dinosaur6. This raises the fundamental question of whether modern birds inherited egg colour from their nonavian dinosaur ancestors, or whether egg colour evolved… 
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