|A neosauropod egg, Western Argentina. Photo: Lucas Fiorelli|
A new study says the colors found in modern birds' eggs did not evolve independently, as previously thought, but evolved instead from dinosaurs.
According to researchers at Yale, the American Museum of Natural History, and the University of Bonn, birds inherited their egg color from non-avian dinosaur ancestors that laid eggs in fully or partially open nests. The researchers' findings appear Oct. 31 in the online edition of the journal Nature.
"This completely changes our understanding of how egg colors evolved," said the study's lead author, Yale paleontologist Jasmina Wiemann. "For two centuries, ornithologists assumed that egg color appeared in modern birds' eggs multiple times, independently."
The egg colors of birds reflect characteristic preferences in nesting environments and brooding behaviors. Modern birds use only two pigments, red and blue, to create all of the various egg colors, spots, and speckles.
"We infer that egg color co-evolved with open nesting habits in dinosaurs," Wiemann said. "Once dinosaurs started to build open nests, exposure of the eggs to visually hunting predators and even nesting parasites favored the evolution of camouflaging egg colors, and individually recognizable patterns of spots and speckles."
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. Like feathers and wishbones, we now know that egg color evolved in their dinosaur predecessors long before birds appeared."
David Varricchio, who studies dinosaur reproduction and brooding at Montana State University in Bozeman, says that because the authors used a novel technique, others will want to test its veracity. But, he says, the fact that we are even beginning to discuss the color of eggs more than 66 million years old is “pretty dang amazing.”
Wiemann plans to increase the dinosaur sample size to see whether she can pin down exactly where and when within the carnivorous theropod group of dinosaurs (which also includes birds) colored eggshells first evolved, and what color came first. Given the analytical methods from other scientific disciplines now available for work on fossils, “It’s an amazing time to be a paleontologist,” she says.
The above story is based on Materials provided by Yale University. Original written by Jim Shelton.