Birds of a Feather

To kick off this blog, I wish my fellow Canucks a happy Canada Day this July 1!

So have you heard? Life is getting increasingly set-in-stone (pardon the pun) for us paleoartists, as paleontologists continue their relentless chipping and chiselling at our artistic license regarding the colors of dinosaurs. Last year, Li et al. (2010) and Zhang et al. (2010) used an ingenious technique to decode the actual colors that the feathered dinosaurs Anchiornis huxleyi and Sinosauropteryx prima sported. By examining the shape and distribution of microscopic (originally pigment-bearing) structures called melanosomes fossilized within the exquisitely preserved plumage of this tiny four-winged troodontid dinosaur, they were able to show that the patterns exhibited by the melanosomes were similar to patterns found in living birds (the probable descendents of a common ancestor with Anchiornis and Sinosauropteryx). Because these patterns correlate with feather color in extant avian species, the investigators were able to map out the actual color patterns of Anchiornis: grey with alternating white strips on the wings, a russet crest and russet markings on the cheeks. This compelled me to update my previously red-colored illustration of the animal, yielding the following:

Anchiornis huxleyi, sporting realistic colors.

Now, a different team of researchers (Wogelius et al., 2011) has applied a brand new technique to shed light on the plumage coloration of the 100-million-year-old early Chinese bird, Confuciusornis sanctus. They reported today in Science Express that x-ray fluorescence images acquired of the magnificently preserved avalian dinosaur fossil reveal the presence of traces of copper in organometallic compounds derived from the pigment eumelanin, which is responsible for dark coloration in skin, fur and feathers. The technique allowed mapping of the distribution of eumelanin over the entire fossil, revealing that Confuciusornis possessed light colored wings and a dark head, neck and tail.

Remarkable discoveries such as this one underscore not only the sheer amount of information preserved within some fossils, but also the ingenuity of paleontologists faced with the task of reconstructing the biology of organisms whose remains have lain sandwiched between sedimentary rock layers for dozens to hundreds of millions of years. Until now, only feathered dinosaurs have been color-mapped, but this is mainly because the analysis was based on the morphological examination of melanosomes within feathers. However, the integument of scaly-skinned animals is also extremely well-preserved in some specimens, and paleontologists such as Phillip Manning are hard at work to determine whether the thin veneer of organic material that sometimes accompanies the skin impressions can be used to infer the original distribution of pigments in life. For example, it will be interesting to determine whether techniques such as synchrotron rapid scanning x-ray fluorescence (SRS-XRF) will yield color patterns on scaly skin impressions of dinosaurs like the mummified Edmontosaurus annectens specimen nicknamed ‘Dakota’. For now, paleoartists wield a measure of artistic license in assigning color patterns to non-feathered dinosaurs, but if recent advances in paleontological analytical techniques are any indication, the relative creative freedom of these days may soon go the way of the dinosaur.

References

Quanguo Li, Ke-Qin Gao, Jakob Vinther, Matthew D. Shawkey, Julia A. Clarke, Liliana D’alba, Qingjin Meng, Derek E. G. Briggs, Long Miao, Richard O. Prum. Plumage Color Patterns of an Extinct Dinosaur. Science, Online February 4, 2010 DOI: 10.1126/science.1186290

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. Trace Metals as Biomarkers for Eumelanin Pigment in the Fossil Record. Science, 2011; DOI: 10.1126/science.1205748

Fucheng Zhang, Stuart L. Kearns, Patrick J. Orr, Michael J. Benton, Zhonghe Zhou, Diane Johnson, Xing Xu, and Xiaolin Wang. Fossilized melanosomes and the colour of Cretaceous dinosaurs and birds. Nature, 27 January 2010

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