Trove of Dinosaur and Bird Feathers Preserved in Amber Offers Novel Evolutionary Insights

An isolated barb from a vaned feather, trapped within a tangled mass of spider’s web in Late Cretaceous Canadian amber. Pigment distribution within this feather fragment suggests that the barb may have been gray or black. Image: Science/AAAS

 
The notion of dinosaur specimens being preserved in amber might call to mind the blockbuster movie Jurassic Park, but feathers encased in amber 70 to 85 million years ago are giving researchers real insight into the evolution of these incredible structures in birds and non-avian dinosaurs.
  
Digging through thousands of chunks of amber from a Late-Cretaceous site in Canada turned up specimens of 11 feathers or protofeathers (some of the most primitive feathers). The fossils show the progression from hair-like filament structures seen in protofeathers of non-avian dinosaurs, to the more complex branching feathers of modern birds. (Scroll down for more images.)
 
“This discovery is a pretty significant find,” University of Alberta paleontologist Ryan McKellar told The Atlantic. “It supports a model for the evolution of feathers that has previously relied on compression fossils that are difficult to interpret and have been hotly debated.”
 
The fingernail-size chunks of amber preserved feather structure and pigmentation in unmatched detail, says McKellar. They support the theory that feathers started off as single, flexible filaments (like those that made up the coat "dino fuzz" covering some dinosaurs), and eventually adapted into branching complex structures for flight and diving.
 
The pigment cells the researchers found suggest that, just like modern birds, the feathered animals might have had a range of transparent, mottled, and diffuse colors.
 
McKellar and his team aren’t yet sure which plumage belonged to birds and which belonged to dinosaurs, but some filament structures contained in the protofeathers are strongly similar to those seen in other non-avian dinosaur fossils, they report in a paper in the current issue of the journal Science.
 
Now, on to the photographs!
 

These filaments are morphologically similar to the protfeathers that have been found as compression fossils associated with some dinosaur skeletons. Pigment distributions within these filaments range from translucent to near-black. Image: Science/AAAS

 
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Cross-section through a feather with basally-coiled barbules (and a bug). The helical coiling is directly comparable to coils found in modern bird feathers specialized for water update. The high number of coils in the amber-entombed feather is suggestive of diving behavior, but similar structures are also used by some modern birds to transport water to the nest. Image: Science/AAAS

 
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Six feather barbs. Localized pigmentation creates a beaded appearance within each barbule: This has implications for the structural interpretation of fossil feathers exhibiting this general morphology. Pigment distribution within the specimen suggests that the feather would have originally been medium- or dark-brown in color. Image: Science/AAAS

 
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The cork-screw shaped structures are the tightly coiled bases of feather barbules. These are interrupted toward the bottom of the image, where they exit the amber piece. Image: Science/AAAS

 
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An isolated barb from a white belly feather of a modern grebe, illustrating coiled barbule bases comparable to those in the Cretaceous specimen. In both cases, the coiling is a structural adaptation that allows the feather to absorb water. Image: Science/AAAS

 
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The brown color is produced by pigments within the amber-encased feather. Image: Science/AAAS

 
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Sixteen clumped feather barbs. Image: Science/AAAS

 
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Six pigmented feather barbs. Image: Science/AAAS

 
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Isolated, unpigmented feather barb and a mite. Image: Science/AAAS

  
Related stories:

Using scanning electron microscopy, researchers found pigment-bearing structures incased in the proto-feathers of non-avian dinosaur fossils.
 
Researchers have identified the colors of individual feathers belonging to Anchiornis huxleyi, a four-winged dinosaur of the late Jurassic.