An isolated barb from a vaned feather, trapped within a tangled mass of spider’s web in Late Cretaceous Canadian amber (specimen UALVP 52820). Pigment distribution within this feather fragment suggests that the barb may have been gray or black.
Credit: Image © Science/AAAS
Overview of 16 clumped feather barbs in Canadian Late Cretaceous amber.
Credit: Image © Science/AAAS
LONDON: Fragments of feathers fossilised in amber 70-85 million years ago provide new evidence for the various stages of feather evolution.
An unusually large number of feathers belonging to dinosaurs and early birds were found in the amber, which preserves the structure and pigment of the feathers in much greater detail than fossils in stone.
Eleven samples, found in a Canadian museum collection, were described today in the journal Science as "the richest amber feather find from the late Cretaceous period," between 65 and 99 million years ago.
"Together, the structure and pigmentation of the specimens provide an interesting snapshot of what feathers looked like at this time, and some of their uses," said lead author and paleontologist Ryan McKellar from the University of Alberta in Canada.
Feather complexity
Modern bird feathers are incredibly complex and understanding how these structures evolved has baffled scientists since the days of Charles Darwin, according to paleontologist Mark Norell, from the American Museum of Natural History in New York, writing in an accompanying article in the same journal.
It is now thought that early simple structures called proto-feathers gradually evolved through five stages into branched structures as seen on modern birds today.
Exactly when and how this process happened is hard to pin down, however, because few feather fossils had been found from the Late Cretaceous period, which is best known for ending with a massive extinction of land and marine species, as well as ending the reign of the dinosaurs.
What's more, those fossils that were from this time were normally squashed flat between layers of sediment, losing their three-dimensional shape.
Amber advantage
Amber, on the other hand, preserves specimens in three dimensions with unmatched detail, but such fossils are rare.
Now, this bumper find is helping to fill in the blanks. It includes examples of all five stages of the evolutionary development of feathers, and the preserved 3-D structure gives a much better picture of what they looked like from all angles.
To get a good look at these tiny fragments of feathers, which were discovered in western Canada and reexamined from museum specimens, McKellar's team used high magnification microscopes, as well as a technology called laser scanning confocal microscopy. This is a technique that uses the specimen's response to laser light in order to observe both chemical composition and 3-D-structural details.
From the pigment residues in the amber, the team was further able to determine that the feathers ranged from almost transparent to dark.
