Dinosaurs put all colored bird eggs in one basket, evolutionarily speaking

Mindy Sparks
November 2, 2018

To study the possibility of a dinosaur origin for bird eggs, the team used Raman spectroscopy, which includes shooting samples with lasers and detecting the wavelengths of the light that bounces back against the shell.

Though most of us are familiar with blue-speckled robin's eggs or golden-brown chicken eggs, the sheer range of colors and patterns on bird eggs is fantastic: they can be brick-red, marbled in patterns that look like the surface of the Moon, or covered in squiggly lines like a Jackson Pollock painting.

"Like feathers and wishbones, we now know that egg colour evolved in their dinosaur predecessors long before birds appeared".

In the eumaniraptorans, the researchers found evidence of a blue-green pigment named biliverdin and a red-brown pigment called protoporphyrin IX structurally integrated into the crystal matrix of the eggshell, as they are with birds. The diversity recovered for dinosaur egg colors mirrors that found for modern bird eggs.

"Here, we're able to show just another case that a lot of characteristics unique to birds have their roots much deeper in dinosaur history", Paleontology Division Chair Mark Norell of the American Museum of Natural History told Gizmodo. So if crocodiles didn't develop colored eggs, maybe the dinosaurs did.

"This completely changes our understanding of how egg colors evolved", said Wiemann, a paleontologist in the Department of Geology & Geophysics at Yale University.

This is also what Wiemann hopes to research next-which theropods had colored eggs and which didn't, and how bird nests correspond to egg color. Recently, the same pigments found in colored bird eggs have been discovered in some fossil dinosaur eggs.

People who are accustomed to see the eggs alone the hen, it is hard to imagine how diverse is their colouring from other birds, from chocolate brown to emerald green, from brick red to bright blue. According to a new scientific report, dinosaurs also invented - or, if you want to get technical, first evolved - eggs of different colors.

Birds evolved from eumaniraptoran dinosaurs in the Jurassic Period.

The dinosaurs with egg color were species that kept their eggs in exposed nests: animals like Deinonychus and some Troodontids, active predators that may have laid nests in small groups but not in vast nesting grounds like some of the duck-billed dinosaurs. That was intriguing. Still, it was just one dinosaur.

"We can fingerprint the pigments", Wiemann said.

Now the researchers have analyzed egg shells from more. "A robin's egg is uniformly blue, but a quail's is spotted and speckled". This is an artist's impression of the oviraptorid dinosaur Huanansaurus ganzhouensis.

Different nesting environments, as well as nesting behaviors, are thought to influence egg color. Birds with white eggs today, such as ostriches, parrots, and some domestic chickens, must have later lost the trait of coloring their eggs through evolution, she says.

GREENFIELDBOYCE: In the journal Nature, they report that they found no pigments in birds' distant dinosaur relatives, such as the groups that include triceratops and the long-necked diplodocus.

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