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Fossil feathers in new Science issue



From: Ben Creisler
bh480@scn.org

The new issue of Science is out online (including announcement of a planet
orbiting a double-star system a la Tatooine) with three articles on
Mesozoic feathers--the article about Confuciusornis has been online since
June.


Mark A. Norell (2011)
Fossilized Feathers.
Science 333(6049): 1590-1591 
DOI: 10.1126/science.1212049 
http://www.sciencemag.org/content/333/6049/1590.summary

Summary
Not long ago, extinct dinosaurs were considered by most as scaly and dull.
All the known fossils of primitive birds (stem avians) could easily fit on
a desk and our only look at Mesozoic [250 to 65 million years ago (Ma)]
feathers (except for a few isolated plumes) was Archaeopteryx, a theropod
dinosaur considered by most to be the most primitive bird (see the figure).
How things have changed--now it would take a warehouse to store all the
feathered Mesozoic stem birds and nonavian dinosaurs that have been
collected from global deposits. Feathered animals abound and extend deep
into nonavian history--even, perhaps, to the base of dinosaurs themselves.
Now, instead of scaly animals portrayed as usually drab creatures, we have
solid evidence for a fluffy colored past. Two reports in this issue, by
McKellar et al. (1) on page 1619 and Wogelius et al. (2) on page 1622,
provide a glimpse of the color patterning in the feathers of ancient birds. 


Ryan C. McKellar, Brian D. E. Chatterton, Alexander P. Wolfe, & Philip J.
Currie (2011)
A Diverse Assemblage of Late Cretaceous Dinosaur and Bird Feathers from
Canadian 
Science 333(6049): 1619-1622 
DOI: 10.1126/science.1203344 
http://www.sciencemag.org/content/333/6049/1619.abstract

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. 


Science 333(6049): 1622-1626 
DOI: 10.1126/science.1205748 
Report 
Trace Metals as Biomarkers for Eumelanin Pigment in the Fossil Record
R. A. Wogelius, P. L. Manning, H. E. Barden, N. P. Edwards, S. M. Webb, W.
I. Sellers, K. G. Taylor, P. L. Larson, P. Dodson, H. You, L. Da-qing, U.
Bergmann (2011)
Science 333(6049): 1622-1626 
DOI: 10.1126/science.1205748 
http://www.sciencemag.org/content/333/6049/1622.abstract

Abstract
Well-preserved fossils of pivotal early bird and nonavian theropod species
have provided unequivocal evidence for feathers and/or downlike
integuments. Recent studies have reconstructed color on the basis of
melanosome structure; however, the chemistry of these proposed melanosomes
has remained unknown. We applied synchrotron x-ray techniques to several
fossil and extant organisms, including Confuciusornis sanctus, in order to
map and characterize possible chemical residues of melanin pigments.
Results show that trace metals, such as copper, are present in fossils as
organometallic compounds most likely derived from original eumelanin. The
distribution of these compounds provides a long-lived biomarker of melanin
presence and density within a range of fossilized organisms. Metal zoning
patterns may be preserved long after melanosome structures have been
destroyed. 


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