Feathered dinosaurs show their true colours

Life

A microscopic technique devised to reveal the colour of fossilised feathers has been applied to a dinosaur for the first time

By James O'Donoghue

27 January 2010

Spot the stripy tail
(Image: Chuang Zhao and Lida Xing)

Tiny organelles known as melanosomes produce the vivid colours found in feathers and hair. Close examination of this zebra finch feather using a scanning electron microscope revealed that sausage-shaped eumelanosomes produce a black hue, while spherical phaeomelanosomes produce an orange-brown colour.
(Image: © University of Bristol)

This photo of a 125-million-year-old fossil of Sinosauropteryx, a flightless, meat-eating dinosaur reveals alternating bands of light and dark feathers running along its head and down the middle of its back. Samples were taken from a dark stripe located at the tail base (see arrow) and from a light stripe. Scanning electron microscopy revealed that dark stripes only contained spherical phaeomelanosomes, indicating that they were orange-brown in colour. In contrast, the light stripes – which contained no melanosomes – were probably white in hue.
(Image: The Nanjing Institute/University of Bristol)

A 125-million-year-old fossil of the bird Confuciusornis. Sampling of tiny colour-bearing organelles throughout its body reveal that the main body region sported black feathers, while the long, narrow tail feathers and wing feathers were orange in colour.
(Image: Institute of Vertebrate Paleontology/University of Bristol)

MEET Sinosauropteryx, a cousin of T. rex and the first dinosaur whose plumage has been brought into dazzling full-colour focus.

The discovery comes thanks to a technique devised last year at Yale University to establish the colour of fossilised bird feathers. It has now been applied to a dinosaur fossil in a breakthrough study that offers the prospect of finally working out what some of the feathered dinos of prehistoric Earth really looked like.

The Yale team used a form of scanning electron microscopy to reveal the iridescent, starling-like colours of feathers from a 47-million-year-old fossil bird (Biology Letters, ). Now of the University of Bristol, UK, and colleagues have applied the technique to Sinosauropteryx fossils from the Jehol formation in Liaoning province, China. This showed the presence of microscopic colour-bearing cell structures known as melanosomes in the 125-million-year-old fossil’s feathers (Nature, ).

The melanosomes had previously been mistaken for the bacteria that often colonise the soft tissues of well-preserved fossils. But Benton’s team found that the pattern of these spherical and sausage-shaped structures was identical to that of melanosomes in modern bird feathers.

The 1.2-metre-long, flightless, meat-eating Sinosauropteryx is the most primitive known feathered dinosaur. It sported a Mohican-style bristly feather crest along the top of its head and down the middle of its back. The new study shows that the feathers on its lemur-like tail formed broad orange and white stripes.

Benton hopes further studies will work out what the head and back feathers look like. He says it should be possible to see melanosomes for many different colours in fossilised dinosaur feathers. “I think we will see a mad rush of work where people will observe fossilised melanosomes all over the place,” he says.

So will Hollywood have to remake Jurassic Park in more accurate colours? Probably not. Feathers are extremely rare in the fossil record, and sampling them for melanosomes does irreversible damage to the fossil. It is therefore likely that only a select few dinosaur fossils will ever be subjected to the technicolor screen test.

Topics: Dinosaurs

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