Archive for January 27th, 2010

Sinosauropteryx was a redhead

Wednesday, January 27th, 2010

Artist recreation of russet SinosauropteryxA study performed on Chinese fossils has established for the first time the color of a dinosaur. Sinosauropteryx, a fast, dog-sized carnivore, was covered in orange “dino fuzz” with white stripes on his tail.

The team identified fossilized melanosomes—pigment-bearing organelles—in the feathers and filament-like structures of fossil birds and dinosaurs from northeastern China.

Found in the feathers of living birds, the nano-size packets of pigment—a hundred melanosomes can fit across a human hair—were first reported in fossil bird feathers in 2008. [...]

These earlier findings proved it was possible for melanosomes from dinosaur times to survive in fossils.

But until now no one had found the pigments in dinosaurs—other than birds, which many paleontologists consider to be dinosaurs. And no one had used melanosome shape and density to infer color.

The team used a scanning electron microscope to examine the feathered dinosaur fossils found in Liaoning Province, China. There has been some question as to whether “dinosaur feathers” were actual precursors to feathers as we know them today, or were instead fossilized internal collagen.

This study puts the controversy to bed quite conclusively. Under the electron microscope, the filaments are full of melanosomes much like modern feathers are. Since melanosomes contain the pigment melanin (hence the name), feather color can sometimes be deduced based on the type of melanin.

The two most common types of melanin found in modern birds are eumelanin, associated with black and grey feathers, and phaeomelanin, found in reddish brown to yellow feathers.

Sinosauropteryx fossil showing stripes on tailMelanosomes of both types were found during the new study, providing “the first empirical evidence for reconstructing the colors and color patterning” in dinosaurs and Chinese fossil birds, Zhang and his colleagues write.

For example, the 125-million-year-old early bird Confuciusornis was found to have color variation between blacks and browns in a single feather. And dark areas in Sinosauropteryx’s tail were “absolutely packed with phaeomelanosomes,” said Benton—a finding that led the team to propose that the dinosaur’s tail was striped with “chestnut to rufous [reddish brown] tones.”

That’s not the final word on dinosaur style, though. Some of the most glorious plumage gets its color from diet. Flamingos are pink because of the carotenoid proteins in the plankton they eat, for instance.

Still, this opens up a lot of doors to move beyond speculation on the question of dinosaur coloration. It’s not just feathered fossils that can provide information, but other melanin-rich tissues like skin and hair.

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