Sinosauropteryx, a turkey-size carnivorous dinosaur, is the first dinosaur—excluding birds, which many paleontologists consider to be dinosaurs—to have its color scientifically established.
In 1996, Sinosauropteryx was also the first dinosaur reported to have feathers. It was found in the Yixian formation, 130- to 123-million-year-old sediments in Liaoning Province in northeast China, which have since produced thousands of apparently feathery fossils.
In a report released online today by the journal Nature, an international team of paleontologists and experts in scanning electron micrography infer that this dinosaur had reddish orange feathers running along its back and a striped tail. (Read the full story: "True Dinosaur Colors Revealed for the First Time.")
Why would a dinosaur need a striped tail? Many birds, the living descendants of non-avian dinosaurs, use brightly colored tails for courtship displays.
The feathers of Sinosauropteryx have been the subject of controversy ever since they were first described.
To the naked eye, the fossilized feathers are fine hairlike filaments that give the impression of being soft and downlike. Some researchers proposed that these structures were not feathers at all, however, but the remains of collagen from inside the tail.
The new study shows that these structures—visible in this fossil Sinosauropteryx as dark patches along the back and tail—are packed with melanosomes, pigment-carrying, sub-cellular structures found in the feathers of living birds but not in collagen.
This strengthens the argument that the fossil hairlike structures are protofeathers, an early stage in feather evolution before feathers had central shafts with vanes out to each side, as seen in modern birds.
Photograph courtesy Institute of Fossil Paleontology and Paleoanthropology, Beijing
The feather of an extinct Confuciusornis bird may have had colors similar to those in this modern feather from a zebra finch, according to the new study.
Feather color in Confuciusornis—an early beaked bird found in 120- to 130-million-year-old fossil beds in Liaoning Province, China—was inferred from microscopic melanosomes preserved in a fossil specimen.
Two types of melanosomes were found. Eumelanosomes (such as the finch eumelanosomes inset at left) are rodlike and associated with the colors black and grey in living birds. Phaeomelanosomes (inset right) are spherical and produce colors ranging from reddish brown to yellow. A lack of melanosomes makes white.
Using a scanning electron microscope, the researchers found that a fossil Confuciusornis feather contained both types of melanosomes and was likely multicolored in life.
Photographs courtesy University of Bristol
Fossil Feather Melanosomes
An international team of researchers reported finding fossilized rod-shaped eumelanosomes, shown here in a scanning electron micrograph, and spherical phaeomelanosomes in 125-million-year-old fossil birds and dinosaurs from China.
Eumelanosomes and phaeomelanosomes are two types of sub-cellular structures called melanosomes that are packed with the dark pigment melanin. A close packing of eumelanosomes from the extinct bird Confuciusornis suggests black was part of its color pattern, the new Nature study says.
Melanosomes are found in abundance within the feathers of living birds, and they have been reported before in fossil feathers. (See "First Proof: Ancient Birds Had Iridescent Feathers.")
This is the first time, though, that melanosomes have been found in the fossilized feathers of non-avian dinosaurs—such as Sinosauropteryx and Sinornithosaurus—and in the exquisitely preserved fossil birds from Liaoning Province, China.
Finding melanosomes in dinosaurs shows that the controversial hairlike structures seen in many feathered dinosaur fossils are indeed related to feathers. Analysis of fossilized melanosomes in creatures that lived and died millions of years ago promises to open up exciting new avenues of research and provide a glimpse into the previously unknown world of prehistoric color. (Related pictures: "Evolution of Dinosaur Art.")