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Re: Archaeopteryx had black feathers



I'm not certain of the answer on that front, but I suspect the melanosomes 
themselves are providing structural support, and the strength of that support 
is related to cross-linking inside the capsule.  However, there may also be 
pigments outside the melanosomes that has more structural importance.  I do 
have a contact that would know the details, and I will see if he can clarify 
for me sometime this week.  I'll post a summary to the DML.

--Mike


On Jan 24, 2012, at 3:23 PM, Jason Brougham wrote:

> Now how does that work when the melanin is restricted to the contents of 
> melanosomes? In other words, how can it cross-link the keratin that makes up 
> the feather structure if the melanin is only inside the capsule - like 
> melanosome? perhaps there is also melanin outside the melanosomes?
> 
> Thanks
> -Jason
> ________________________________________
> From: owner-DINOSAUR@usc.edu [owner-DINOSAUR@usc.edu] on behalf of Habib, 
> Michael [MHabib@Chatham.edu]
> Sent: Tuesday, January 24, 2012 3:02 PM
> To: erikboehm07@yahoo.com
> Cc: dinosaur@usc.edu; "bcreisler@gmail.com"@listproc.usc.edu
> Subject: Re: Archaeopteryx had black feathers
> 
> Many of the true pigments (as opposed to structural coloration), particularly 
> melanin, provide improved chemical cross-linking within the integumentary 
> structures they invest.  As a result, pigment-carrying feathers, scales, and 
> hair, particularly those that carry melanin, resist buckling, bending, and 
> abrasion more effectively than the equivalent structures without pigments.
> 
> Whether or not being more rigid and resistant to abrasion is an advantage, of 
> course, depends on the circumstances and usage of the structure in question.  
> Sometimes greater compliance is more advantageous than high rigidity.
> 
> Cheers,
> 
> --Mike
> 
> 
> On Jan 24, 2012, at 1:57 PM, Erik Boehm wrote:
> 
>> Wait a minute,Can someone explain to me what structural properties melanin 
>> has?
>> I thought it was a mere pigment, with no real structural properties as you 
>> find in Keratin of Chitin.
>> So can someone explain to me what they mean by:"the extensive melanization 
>> would have provided
>> structural advantages to the Archaeopteryx wing feather"?
>> 
>> --- On Tue, 1/24/12, Ben Creisler <bcreisler@gmail.com> wrote:
>> 
>> From: Ben Creisler <bcreisler@gmail.com>
>> Subject: Archaeopteryx had black feathers
>> To: dinosaur@usc.edu
>> Date: Tuesday, January 24, 2012, 9:57 AM
>> 
>> From: Ben Creisler
>> bcreisler@gmail.com
>> 
>> 
>> A new online article in Nature Communications:
>> 
>> 
>> Ryan M. Carney, Jakob Vinther, Matthew D. Shawkey, Liliana D'Alba &
>> Jörg Ackermann (2012)
>> New evidence on the colour and nature of the isolated Archaeopteryx feather.
>> Nature Communications 3 (637)
>> doi:10.1038/ncomms1642
>> http://www.nature.com/ncomms/journal/v3/n1/full/ncomms1642.html
>> 
>> 
>> 
>> Archaeopteryx has been regarded as an icon of evolution ever since its
>> discovery from the Late Jurassic limestone deposits of Solnhofen,
>> Germany in 1861. Here we report the first evidence of colour from
>> Archaeopteryx based on fossilized colour-imparting melanosomes
>> discovered in this isolated feather specimen. Using a phylogenetically
>> diverse database of extant bird feathers, statistical analysis of
>> melanosome morphology predicts that the original colour of this
>> Archaeopteryx feather was black, with 95% probability. Furthermore,
>> reexamination of the feather's morphology leads us to interpret it as
>> an upper major primary covert, contrary to previous interpretations.
>> Additional findings reveal that the specimen is preserved as an
>> organosulphur residue, and that barbule microstructure identical to
>> that of modern bird feathers had evolved as early as the Jurassic. As
>> in extant birds, the extensive melanization would have provided
>> structural advantages to the Archaeopteryx wing feather during this
>> early evolutionary stage of dinosaur flight.
>> 
>> 
>> 
>> News stories:
>> 
>> http://www.physorg.com/news/2012-01-winged-dinosaur-archaeopteryx-flight.html
>> 
>> 
>> http://news.brown.edu/pressreleases/2012/01/archaeopteryx
> 
> Michael Habib
> Assistant Professor of Biology
> Chatham University
> Woodland Road, Pittsburgh PA  15232
> Buhl Hall, Room 226A
> mhabib@chatham.edu
> (443) 280-0181
> 

Michael Habib
Assistant Professor of Biology
Chatham University
Woodland Road, Pittsburgh PA  15232
Buhl Hall, Room 226A
mhabib@chatham.edu
(443) 280-0181