The rainbow of hues seen in modern bird eggs probably evolved into dinosaur ancestors of birds that had eggs with colorful and speckled shells.
This corresponds to a new study of fossil eggs in the journal Nature ]. The researchers found that the nearby dinosaurs of birds had eggs with traces of two pigments – one reddish-brown and one blue-green. This same pigment pair mixes and fits into today's bird eggs to create colors that range from robin blue over red to yellow to green.
"There is a wide variety of egg colors and patterns, and for a long time people have guessed that the color of the eggs is a feature that is unique to our modern birds," says Jasmina Wiemann, paleontologist at Yale University , She assumes that the closest living relatives of the birds, the crocodiles, have "completely undyed, non-pigmented eggs."
To see if colored eggs could actually go back in history, she and her colleagues began to do so Oviraptor eggs – a relatives of the Velociraptor, who became famous in the film Jurassic Park.
"This dinosaur is particularly interesting because oviraptors are the first dinosaurs to build open nests," she explains, the earlier dinosaurs buried eggs underground, where the color would make no difference.
"When you start building an open nest, your eggs are exposed to the environment," she notes. There, colors and patterns could camouflage or help dinosaurs recognize their own eggs.
In her 66-million-year-old Oviraptor egg fossils, her team found small concentrations of both pigments staining modern bird eggs. That was fascinating. Still, it was just a dinosaur.
Now researchers have analyzed egg shells from more. "We've been trying to capture the main branches of dinosaurs to get a good idea for all non-bird dinosaurs," she says.
They found no pigments in the distant birds of dinosaurs, such as. For example, in the groups that include Triceratops and Langer Diplodocus.
However, the reddish-brown and cyan pigments were contained in egg shells from the group of dinosaurs that includes birds and their close relatives. These pigments were incorporated into the shells in the same sophisticated manner as in modern bird eggs – and Wiemann believes that this can not be a coincidence.
"We very likely have a single evolutionary origin of the egg color," she says.
In addition, analysis of pigments showed that dinosaur eggs even had spots and spots. And that surprised Mark Hauber, an ornithologist and expert on eggs at the University of Illinois, Urbana-Champaign.
"Not only do we now know that dinosaur eggs were colorful, they were speckled, which represents a very different aspect of diversity," says Hauber.
Dinosaurs may have needed these fancy eggs for the same reasons as birds, suggesting that their behavior could have been just as complex.
"Dinosaur eggs could be disguised, they could be individually recognized, they could be mimetic," says Hauber. "So, there are all the functions associated with recognizing patterns on eggs that we did not even consider for dinosaur eggs."
In addition, according to Hauber, different colors and markings may have been associated with some dinosaur-related dinosaur shops that we have never even thought of. A certain egg color could have warned potential predators of danger, he says, "and that could be that the mother's dinosaur is coming back or the dad dinosaur is coming back and beating you."