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Blue-green oviraptor dinosaur eggs (free pdf)

Ben Creisler

New in preprint PeerJ in open access:

Jasmina Wiemann, Tzu-Ruei Yang, Philipp N. N Sander, Marion Schneider,
Marianne Engeser, Stephanie Kath-Schorr, Christa E Müller & P. Martin
Sander (2015)
The blue-green eggs of dinosaurs: How fossil metabolites provide
insights into the evolution of bird reproduction.
PeerJ PrePrints 3:e1323
doi: https://dx.doi.org/10.7287/peerj.preprints.1080v1

Open-nesting birds use biological pigments in eggshell to camouflage
their unhatched offspring, varying the colour to account for the
nesting environment and location. The tetrapyrrolic pigments
protoporphyrin (PP) and biliverdin (BV), which both participate in the
haem metabolism, are responsible for the reddish brown of chicken eggs
and the brilliant blue of robin and emu eggs. However, eggshell
pigmentation correlates with the nest type in a wide range of avian
species and suggests that coloured eggs are basal to the avian
lineage, extending back to their non-avian dinosaur origins. Detecting
preserved eggshell pigments could thus shed light on dinosaur nesting
behaviour. Using HPLC separation coupled to ESI-Q-TOF mass
spectrometry, we here provide the first record of the eggshell
pigments PP and BV preserved in fossils from three different
localities, in 66 million year-old oviraptorid eggshell (Macroolithus
yaotunensis). These eggs were presumably laid in at least partially
open nests by the oviraptorid Heyuannia huangi and camouflaged by an
originally blue-greenish egg colouration. Such a blue-greenish
eggshell pigmentation hints at increased paternal care in Heyuannia.
Shell porosity measurements, preserved clutches and parental animals
support an open nesting behaviour for oviraptorid dinosaurs.
Furthermore, the detection of PP, together with supporting microscopic
observations, represents the first evidence for cuticle preservation
in fossil eggshell. Our study demonstrates that molecular biomarkers,
such as preserved metabolites, can be used to trace the evolution of
modern avian traits, and to provide insights into dinosaur
reproductive biology and the preservation of endogenous organic matter
in fossil vertebrates.