RE: Archaeopteryx had black feathers

[Jason Brougham <jaseb@amnh.org>]

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 
> 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