Science 16 September 2011:
Vol. 333 no. 6049 pp. 1619-1622
DOI: 10.1126/science.1203344

"A Diverse Assemblage of Late Cretaceous Dinosaur and Bird Feathers from Canadian Amber"

Ryan C. McKellar, Brian D. E. Chatterton, Alexander P. Wolfe, Philip J. Currie


Abstract:
The fossil record of early feathers has relied on carbonized compressions that lack fine structural detail. Specimens in amber are preserved in greater detail, but they are rare. Late Cretaceous coal-rich strata from western Canada provide the richest and most diverse Mesozoic feather assemblage yet reported from amber. The fossils include primitive structures closely matching the protofeathers of nonavian dinosaurs, offering new insights into their structure and function. Additional derived morphologies confirm that plumage specialized for flight and underwater diving had evolved in Late Cretaceous birds. Because amber preserves feather structure and pigmentation in unmatched detail, these fossils provide novel insights regarding feather evolution.

The currently accepted (11, 12) evolutionary-developmental model for feathers (Fig. 1A) consists of a stage I morphology characterized by a single filament: This unfurls into a tuft of filaments (barbs) in stage II. In stage III, either some tufted barbs coalesce to form a rachis (central shaft) (IIIa), or barbules (segmented secondary branches) stem from the barbs (IIIb); then, these features combine to produce tertiary branching (IIIa+b). Barbules later differentiate along the length of each barb, producing distal barbules with hooklets at each node to interlock adjacent barbs and form a closed pennaceous (vaned) feather (stage IV). Stage V encompasses a wide range of additional vane and subcomponent specializations. Most modern birds possess stage IV or V feathers or secondary reductions from these stages (11, 16). Modern feathers exhibit a range of morphologies that are associated with their various functions and remain discernible in some of their finest subunits, the barbules (17). This is particularly important in the study of amber-entombed feathers because preservation is biased toward feather subcomponents, which provide the basis for our morphological comparisons.

Canadian amber provides examples of stages I through V of Prum’s (11) evolutionary-developmental model for feathers. None of the additional morphotypes observed in compression fossils of nonavian dinosaurs (8, 15) or amber (4) were found here, suggesting that some morphotypes may not represent distinct evolutionary stages, or may not have persisted into the Late Cretaceous. The snapshot of Campanian feather diversity from Canadian amber is biased toward smaller feathers, subcomponents of feathers, feathers that are molted frequently, and feathers in body positions that increase their likelihood of contacting resin on tree trunks. Despite these limitations, the assemblage demonstrates that numerous evolutionary stages were present in the Late Cretaceous, and that plumage already served a range of functions in both dinosaurs and birds

quisquose wrote:Amazing.

I listened to this news on Radio 4 this morning. I just had to stop what I was doing (half shaved), and listen in awe.

Then I felt an enormous sadness at the thought that, whilst I was thrilled at the news, a significant percentage of the population was likely to be shaking their heads and muttering "it's all lies".

theropod wrote:No, I'm not suggesting a "jurrasic park" remake.

quisquose wrote:Then I felt an enormous sadness at the thought that, whilst I was thrilled at the news, a significant percentage of the population was likely to be shaking their heads and muttering "it's all lies".

ughaibu wrote:

quisquose wrote:Then I felt an enormous sadness at the thought that, whilst I was thrilled at the news, a significant percentage of the population was likely to be shaking their heads and muttering "it's all lies".

I dont think I've ever met an evolution denier in the UK. Is there a documented significant percentage?

Shrunk wrote:

ughaibu wrote:

quisquose wrote:Then I felt an enormous sadness at the thought that, whilst I was thrilled at the news, a significant percentage of the population was likely to be shaking their heads and muttering "it's all lies".

I dont think I've ever met an evolution denier in the UK. Is there a documented significant percentage?

This poll suggests the prevalence is not much different than that of the US:

http://www.telegraph.co.uk/news/religio ... ution.html

Samples of amber in western Canada containing feathers from dinosaurs and birds have yielded the most complete story of feather evolution ever seen.

Eleven fragments show the progression from hair-like "filaments" to doubly-branched feathers of modern birds.

The analysis of the 80-million-year-old amber deposits is presented in Science.

The find, along with an accompanying article analysing feather pigment, adds to the idea that many dinosaurs sported feathers - some brightly coloured.

A second paper in Science examines another aspect of the ornamentation: colour.

Feathers are given their colour by structures in their cells called melanosomes, which contain melanin, the same chemical that produces our skin colour.

Study of remnants of these melanosomes has already yielded evidence, for example, that one of the first feathered dinosaurs ever discovered, the Sinosauropteryx, was a "redhead".

But usually, the melanosomes of feathers, or the melanin they leave behind, are destroyed with time, leaving few clues as to what colour a given dinosaur would have been.

Now Roy Wogelius of the University of Manchester in the UK has developed a method using high-energy rays of light from a synchrotron that can spot tiny amounts of metal atoms left behind by eumelanin, one of the types of melanin responsible for a range of black and brown colours.