Pictures: Evolution of Dinosaur Art

Feathered Fossil?

Photograph by O. Louis Mazzatenta, National Geographic Stock

The fossil of Sinosauropteryx revealed in 1996, above, was so well preserved that hairlike structures were apparent all over its body. These showed up as dark areas, particularly along the back and tail.

Researchers assumed that the whole animal had been covered in these short filaments. Many paleontologists suggested the structures were protofeathers, the evolutionary precursors to the type of feathers seen commonly on birds today.

Some researchers weren't convinced and suggested that the structures were the fossilized remains of collagen that was originally inside the dinosaur's body, not outside, as feathers would be. (Related: "'Feathered' Dinosaur Was Bald, Not Bird Ancestor, Controversial Study Says.")

If the structures on Sinosauropteryx proved to be protofeathers—as the January 2010 study, among others, suggests—it would mean that a whole group of animals that were evolutionarily more "modern," or derived, than Sinosauropteryx, including Tyrannosaurus rex, could have had feathers.

(Related quiz: Test your dinosaur IQ.)

Published January 27, 2010

Color, Hiding in the Dark

Photograph by O. Louis Mazzatenta, National Geographic Stock

A detail of the hairlike structures in the fossil of Sinosauropteryx gives the impression that they were soft and downlike. Close examination of the dark areas revealed microscopic structures that were initially interpreted as fossilized bacteria.

The January 2010 report shows that these structures are actually melanosomes, a subcellular structures that contain the pigment melanin.

Since the feathers of living birds are known to contain melanosomes, it's highly likely that these structures are related to feathers and are perhaps protofeathers, an early stage in feather evolution before feathers had a central shaft with vanes out to each side, as seen in modern birds.

Published January 27, 2010

Running Naked

Painting by Roy Andersen, National Geographic Stock

A Deinonychus (illustrated in a 1978 National Geographic magazine) may look more like a running lizard than a bird, but the dinosaur played a key role in convincing many researchers that birds descended from dinosaurs.

The concept that dinosaurs had a close evolutionary relationship with birds dates back to at least the 19th century, when British naturalist Thomas Huxley proposed the idea after the discovery of the earliest known fossil bird, Archaeopteryx.

The bird-dinosaur theory was revived in earnest in the 1960s and '70s by John Ostrom of Yale University, who studied the fossil skeleton of Deinonychus and found trait after trait that linked the North American dinosaur to birds.

Still, artistic reconstructions of even the most birdlike dinosaurs took a while to become very birdlike—and to put feathers on a dinosaur seemed extremely speculative until relatively recently.

(Related pictures: "What's Wrong With This Picture? An Audio Critique [of Dinosaur Art].")

Published January 27, 2010

Featherless in Art, If Not Life

Illustration by John Sibbick, National Geographic Stock

This illustration of an adult Oviraptor feeding its young, which appeared in National Geographic magazine in 1996, was prepared just before the discovery of feathers on dinosaurs. Ironically, the point of the picture was to show how birdlike dinosaurs were.

The 1996 National Geographic article reported on a wonderfully preserved, egg-filled nest found in Mongolia with an adult Oviraptor nesting right on top of it.

Even though the Oviraptor parent's arms were found spread outward, as if to cover the eggs with feathery arms—as living nesting birds do—National Geographic editors opted to show the dinosaur and its hatchlings featherless.

Published January 27, 2010

Downy-Soft T. Rex Hatchling

Illustration by Michael Skrepnick, National Geographic Stock

As more and more evidence piled up to support the idea that dinosaurs were not only related to birds but had feathers, artists and scientists began to feel more comfortable creating scenes including feathery dinosaurs like the hatchling Tyrannosaurus rex in this 1999 National Geographic magazine illustration.

There were two main reasons why National Geographic commissioned this art despite the fact that, as of 1999, no tyrannosaur had been found with feathers—that would come later, in 2004. (See "New Dinosaur Discovered: T. Rex Cousin Had Feathers.")

First, tyrannosaurs were evolutionarily more "modern" than Sinosauropteryx—so if Sinosauropteryx had feathers, so could T. rex. Second, since most of the feathered dinosaurs that had been found thus far were small, the function of feathers may have been to keep small dinosaurs, like baby tyrannosaurs, warm.

Published January 27, 2010

Earliest Known Bird

Photographs by O. Louis Mazzatenta, National Geographic Stock

The first fossil of Archaeopteryx was a lone feather found fossilized in a limestone quarry in Germany in 1860 (left). It was only later that many specimens of the crow-size Archaeopteryx were found with fossilized bones and preserved impressions of feathers, such as this full-body fossil (right) found nearby in 1861.

Many very birdlike feathered dinosaurs have since been discovered in the 131- to 120-million-year-old Jehol Group sediments of China since 1996, when Sinosauropteryx was reported. These new specimens have raised important questions about the origins of feathers, birds, and flight.

With the January 2010 announcement that melanosomes have been found in fossil feathers, many museum drawers around the world will be opened to check for fossils—perhaps including Archaeopteryx fossils—that might have fossilized pigment.

Published January 27, 2010

Archaeopteryx in 1940s Finery

Illustration by Charles R. Knight, National Geographic Stock

When paleoartist Charles Knight painted this portrait of Archaeopteryx with a pterosaur for National Geographic in 1942, little did he know that someday scientists would actually have a way to deduce the colors of extinct animals.

To reconstruct the colors of ancient animals, scientists and paleoartists had to do a lot of educated guesswork, mostly based on their familiarity with living species.

With the discovery of pigments in dinosaur fossils, much of the guess work in reconstructing color, at least in well-preserved species, will disappear.

Even a pterosaur, shown here as a drab reptilian creature, will have a chance to be colorful—many well-preserved specimens show hairlike structures similar to those in some dinosaurs fossils.

Published January 27, 2010

Best Guess, Circa 1996

Photograph by O. Louis Mazzatenta, National Geographic Stock

The discovery of melanosomes in fossil birds and dinosaurs, announced in January 2010, may help determine some colors in prehistoric feathers—such as the the speculative blacks and browns on this 1996 model of the feathered dinosaur Caudipteryx zoui.

But not all feather color is produced by melanosomes. Some colors—such as the pink in flamingo feathers and the bright yellow of canaries—are produced by the food animals eat.

So far, there's no proven way of detecting signs of those types of colors in fossils. In the future, however, that may be possible as efforts to study the chemical compositions of fossils continue. Future studies may also reveal the colors of other melanin-containing coverings, such as skin and hair, and perhaps even the color of eyes.

Published January 27, 2010

Oviraptor Makeover

Illustration by Luis Rey

This feathery scene created in the late 2000s shows what look like giant turkeys facing off against a menacing meat-eater. It also shows how far paleoartists have come in their depictions of birdlike dinosaurs.

The turkey-like creature is actually the giraffe-size oviraptor, Gigantoraptor, whose discovery was announced in 2007. (See more pictures of Gigantoraptor and learn about its discovery.) Although no feathers were found preserved with the Gigantoraptor fossil, feathers have been found on closely related dinosaurs, such as Caudipteryx (see picture).

Note that the artist, Luis Rey, has put feathers on large animals. This is a reflection of the fact that long, filamentous feathers are being found on larger and larger dinosaurs, such as Beipiaosaurus (see picture), suggesting that feathers had other functions in nonflying dinosaurs than keeping the little ones warm.

Even though the color is guesswork, illustrations like this, showing very birdlike, colorful dinosaurs, are now mainstream. This artwork, for example, won the 2009 Lanzendorf Prize, the highest award for paleoart given annually by the Society of Vertebrate Paleontology.

Stay tuned to see how the new science-based determination of color in dinosaurs, birds, and other creatures will impact our understanding of the role of color among extinct animals and our view of prehistoric times.

Get the story behind the story from author Chris Sloan >>

Published January 27, 2010