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Re: Moyer et al.: a good study, but not the last word



Agree on the symmetry although Greg Paul's point about colors is also worth keeping in mind. Even if they are melanosomes in some cases does not mean that they are melanosomes in all cases. I would be surprised if there were not abundant examples of each.

Dan

. On 3/7/2014 10:56 AM, don ohmes wrote:


True, but as Holtz points out, bilateral symmetry (whether dorsal / ventral or 
right / left) would be unlikely in the bacterial case.

Which reminds me -- does asymmetrical pigmentation exist in extant birds?

------------------------------
On Fri, Mar 7, 2014 9:18 AM EST Dan Chure wrote:

And of course, some specimens might be bacteria and some might be
melanosomes. This is not an all or nothing game.

Dan



On 3/7/2014 5:50 AM, Thomas R. Holtz, Jr. wrote:
Greetings,

Just a few notes to add to the comments on the new Moyer et al. paper on 
bacteria vs. melanosomes:

There are some good observations in this. However, I think it is fair to say 
this is not the final word on the subject. I know that
the UT Austin group that has previously published on melanosomes (including a 
former student) are hard at work on new studies which
point to the paleo-examples as being actual melanosomes, and I await news from 
Jakob Vinther's lab.

Regardless of the final truth, this is good for science: we have to test our 
claims!!

Towards that end, a test I'd like to see. In crystal-level geochemical studies, 
it is standard operating procedure to publish
"sample maps" of the crystal being probed, for verification and replication 
purposes. I do not recall seeing these for the previous
melanosome studies. That might help to give confidence that a pattern of color 
was real, and thus probably original rather than
postmortem bacterial growth. For instance: tracing down and across both left and right 
"wings" of Anchiornis and find the same
distribution of supposed-white and supposed-black patterns would increase our 
confidence in their reality.

Take care,

Thomas R. Holtz, Jr.
Email: tholtz@umd.edu   Phone: 301-405-4084
Office: Centreville 1216                        
Senior Lecturer, Vertebrate Paleontology
Dept. of Geology, University of Maryland
http://www.geol.umd.edu/~tholtz/
Fax: 301-314-9661               

Faculty Director, Science & Global Change Program, College Park Scholars
http://www.geol.umd.edu/sgc
Fax: 301-314-9843

Mailing Address:        Thomas R. Holtz, Jr.
                        Department of Geology
                        Building 237, Room 1117
                        University of Maryland
                        College Park, MD 20742 USA






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