Research

Dinosaurs Put All Colored Birds' Eggs in One Basket, Evolutionarily Speaking

Dinosaurs Put All Colored Birds' Eggs in One Basket, Evolutionarily Speaking

On the other hand, recent findings suggest that the dinosaurs could lay eggs of different colors. It's the textured gray fossil on the far right, surrounded by (clockwise from bottom right) a green cassowary egg, a blue-gray emu egg, and a white alligator egg.

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 awesome: 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.

Co-author Mark Norell, the Macaulay Curator of Paleontology at the American Museum of Natural History, noted that "Colored eggs have been considered a unique bird characteristic for over a century". Those colors and variations, according to a new study published Wednesday in the journal Nature, share a common origin.

Study author Jasmina Wiemann, now a doctoral student at Yale University, began her search for colorful eggs with a dinosaur named Heyuannia huangi, an oviraptor with a beak like a parrot's.

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.

The team found fossil eggs of many colors and speckling patterns. "Like feathers and wishbones, we now know that egg color evolved in their dinosaur predecessors long before birds appeared". This made scientists wonder whether birds evolved colored eggs on their own, or whether they inherited egg color from an ancient ancestor. That study raised a question about whether the colors of bird eggs can be traced to a dinosaur origin or if they evolved on their own.

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In the eumaniraptorans, the researchers found evidence of a blue-green pigment called biliverdin and a red-brown pigment called protoporphyrin IX structurally integrated into the crystal matrix of the eggshell, as they are with birds. However, they needed to find a new method that wouldn't jeopardize the fossils. Colors and patterns may have helped camouflage eggs that were newly exposed to predators, or allowed parents to recognize their soon-to-be hatched offspring, as is believed to be the case with modern bird eggs. They discovered that some branches of the dinosaur tree had no pigment on their eggs, including sauropods and many other large, four-legged species.

But, once again, birds are living dinosaurs.

And, she said, "It's an example of another feature that was really thought to be exclusive among birds".

Traditionally, dinosaurs were thought of as reptilian-style breeders that dumped their eggs and left.

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. Other scientists told her she was "wasting her time", she said, because they assumed dinosaur eggs lacked pigment. Given the analytical methods from other scientific disciplines now available for work on fossils, "It's an awesome time to be a paleontologist", she says.