The finding of melanosomes, or pigment-bearing organelles, embedded in the fossil feathers of select dinosaur specimens has unexpectedly provided a means to reconstruct a wide array of feathered dinosaurs with a scientifically precise palette.
“There is a correlation between the shape and size of these melanosomes and the coloring produced on the feather,” said Xu Xing, a scholar at the Institute for Vertebrate Paleontology and Paleoanthropology in Beijing.
Scientists in Beijing and Bristol are now using a newfound technique to restore the colors of long-extinct feathered dinosaurs that have been uncovered over the past decade in northeastern China. They were preserved in remarkable detail, Xu explained, in part through the fortuitous eruption of volcanoes that periodically encased winged dinosaurs, pterosaurs and birds in ash, in what is now the Chinese province of Liaoning.
“Spectacular fossils from the Early Cretaceous Jehol Group of northeastern China have greatly expanded our knowledge of the diversity and palaeobiology of dinosaurs and early birds, and contributed to our understanding of the origin of birds, of flight, and of feathers,” stated Zhou Zhonghe, acting director of the prestigious Institute for Vertebrate Paleontology and co-author of a recent paper on the fossil feather breakthrough for the British journal Nature.
The examination of a sampling of dinosaur fossils from the Jehol Group using a scanning electron microscope at the University of Bristol uncovered the color-triggering melanosomes, Zhou said. In the future, entire reconstructions across a full-color spectrum could be created of dinosaurs featuring pennaceous feathers, or those with a central shaft and lateral vanes that resemble the flight feathers of modern birds, he explained. These might include the oviraptorosaur Caudipteryx and the dromaeosaurid Microraptor gui.
They could also extend to theropod dinosaurs that featured more primitive protofeathers, such as Sinosauropteryx, Sinornithosaurus and Beipiaosaurus, he said.
“We have discovered nearly 30 different birds and over a dozen feathered dinosaurs from the Mesozoic of China,” Zhou noted. “Potentially, we will be able to discover melanosomes in all of these, considering their exceptional preservation.”
And the quest to resurrect these feathered species, he added, will ultimately be expanded. For instance, the U.S.-educated Zhou said, “Some pterosaurs are known to have hair-like integuments, and we would be very interested to discover if their integuments could be protofeathers as well.”
“And it would be interesting also to examine the hair of mammals from the same deposits,” he said.
Mike Benton, a professor of paleontology at the University of Bristol who co-wrote the “Fossilized Melanosomes and the Color of Cretaceous Dinosaurs and Birds” study, said in an interview by electronic mail: “We have been working between Beijing and Bristol for four years now, initially on preservation of the birds and dinosaurs - and other fossils.”
“The project then covers questions about the chemistry of the fossils, and of the initial burial conditions,” Benton said.
“As for melanosomes, we also wish to look in much more detail at as many of the Jehol, and other, exceptionally preserved birds and dinosaurs as we can.”
“Our main motivation is to understand the place of melanosomes and of color in the evolution of theropod dinosaurs and birds, said Benton. “If, as seems to be the case, early theropods had rather striking color patterns, this suggests a key early function of feathers was display.”
“Reconstruction of color patterns,” Benton stated in the paper, “will also inform debates on the functions of feathers in non-avian dinosaurs, whether primarily for thermoregulation, camouflage or communication.”
Meanwhile, Jakob Vinther, a scholar at Yale University who headed a parallel study titled “Plumage Color Patterns of an Extinct Dinosaur” for the journal Science, said in an interview that he is now in the process of refining the technique to correlate varying melanosomes with different colors: “We want to make the method better, partly by putting modern feathers into the modeling.”
Vinther, the first to discover that fossil feathers preserve melanosomes and the first to map out the resulting colors in a fossil of the four-winged Anchiornis, said that a reconstruction of the hues and patterning for the 155-million-old dinosaur showed that it likely “used its colors and feathers for sexual attraction, just like modern birds.”
“Modern birds have a lot of variety in colors and color patterns – this could be similar to feathered dinosaurs,” he said.
Vinther also said that the melanosomes preserved in volcanic ash for more than a million centuries and those found in modern birds are virtually identical, and added that there are likely to be frequent echoes in the coloring of birds and terrestrial dinosaurs.
“The plumage color pattern elements of the Late Jurassic Anchiornis,” Vinther stated in the Science study, “are strikingly similar to various living birds including domesticated fowl providing insights into the evolution of feather pigment pattern development.”
“We did in our current paper actually develop a statistical method to predict colors of dinosaurs,” Vinther added in an interview.
Xu Xing, who has been a leading proponent of the theory that Jurassic dinosaurs gave rise to birds, said that many more new specimens of feathered theropods are likely to be unearthed in China over the next decade. “Feathers,” he said, “could be a defining feature for a whole class of dinosaurs or even a larger group including all dinosaurs and pterosaurs.”
The IVPP’s Zhou added that as technological advances allow scientists to sculpt the colors and contours of winged theropods and birds with ever-greater verisimilitude, books and images on the subject produced even a few years ago might have to be comprehensively redrafted or simply burned: “I expect the work by us and other groups in the near future will significantly change our view of what the feathered animals looked like in real life.”
Might it one future day be possible to recover not just coloring information, but also genetic material in a bid to reconstruct the genome of one or more dinosaur species?
“If you consider birds as dinosaur species, it might be possible soon,” Zhou said. “However, in term of Mesozoic dinosaurs, I am not aware of any convincing evidence of DNA preservation.”
Xu concurred: “It is unlikely that scientists will ever be able to reconstruct the entire genome sequencing for even one species of an extinct dinosaur.”
Yet with steady advances in understanding the morphology of dinosaurs and in genomics, he forecast, “It might one day be possible to genetically engineer new species that resemble any given dinosaur.”
Kevin Holden is a writer who has covered China's latest dinosaur discoveries for National Geographic News and for EurekAlert! Chinese.