Lots of creatures lay eggs nowadays - reptiles, birds, and some fish - but only birds lay colored ones. Two, some parent birds use spot patterns to recognize their own eggs if they live in large colonies (or to prevent freeloading birds, like cuckoos, from sneaking their eggs into a brood).
In spite of their diversity, bird eggs derive their color from just two pigments: protoporphyrin, which produces a reddish-brown color, and biliverdin, which creates blue and green.
Birds, odd as it seems, are living dinosaurs, the last of a lineage that otherwise went extinct 66 million years ago.More news: Federer to play in Paris Masters
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. Not only that, the researchers could see that some eumaniraptoran eggs were spotted and speckled.
What's more, the analysis of pigments showed that dinosaur eggs even had spots and speckles.More news: World's last wilderness areas may vanish
As the researchers write today in Nature, the fact that they found colored eggs in so many carnivorous theropod dinosaurs that are closely related to birds-and exactly the same method of eggshell pigmentation-means colored eggs evolved "deep within the dinosaur tree and long before the spectacular radiation of modern birds", likely more than 150 million years ago. However, they needed to find a new method that wouldn't jeopardize the fossils.
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. 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.
Traditionally, dinosaurs were thought of as reptilian-style breeders that dumped their eggs and left.
Other features which were once assumed to have originated in birds, like wishbones and feathers also came from their dinosaur forebears, Norell said.More news: Brazil joins USA , to move embassy to Jerusalem
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. Given the analytical methods from other scientific disciplines now available for work on fossils, "It's an fantastic time to be a paleontologist", she says.