Dinosaur eggs are usually represented such as the way the film Jurassic Park did back in the day, such as with a relatively elongated shell which is just an ordinary white. But it seems that the reality is quite different. Thanks to the discovery of fossilised pigments, researchers have revealed the astonishing colours that these ancient eggs had.
An inherited or developed trait?
Among oviparous creatures, it seems that birds are the only ones who lay coloured eggs. It was not entirely improbable that this trait originated with their ancestors, the dinosaurs. The first signs suggesting such a phenomenon only appeared last year.
PhD student Jasmina Wiemann from Yale University and her colleagues then announced the discovery of the pigments responsible for the blue-green hue of the fossilised shells of several oviraptors, feathered non-avian dinosaurs who have similarities to birds. Were the coloured eggs of birds due to a distant heritage, or had birds and dinosaurs developed this trait independently? This question has now been answered.
Bird pigments and dino pigments
In this new study, Wiemann and her team analysed the chemical composition of the eggs of 19 bird species, crocodilians and non-avian dinosaurs, in order to identify the pigments involved in their coloration. Biliverdin and protoporphyrin IX, the two pigments responsible for the hue of bird eggs, were also present in non-avian dinosaur shells.
According to the researchers, this trait has evolved only once, and then has been transmitted over millions of years, from the Eumaniraptor group to modern birds.
‘The discovery of a unique origin of the colour of eggshells in dinosaurs is a fantastic reminder that birds have inherited many traits from their dinosaur ancestors,’ said Mary Stoddard from Princeton University, which did not participate in the study. But there is better still.
An unexpected explanation
Indeed, this discovery could also teach us more about how dinosaurs took care of their eggs. In 1990, a fossilised dinosaur was discovered near an egg-filled nest, making headlines and showing for the first time that adults most likely hatched their own offspring. She was then nicknamed Big Mama by the researchers before some clues revealed that it was actually a male, a Big Papa.
This reversal of the situation might have been surprising, however in birds, the blue colour of an egg can signal the quality of the mother's genetic material and hence that of her offspring, and therefore encourage the father to remain near the nest and participate in brooding to protect his offspring. If some dinosaurs lay blue eggs, the discovery of a father hatching the eggs actually makes a lot of sense.