Sinosauropteryx filament melanosomes challenged

[bh480@scn.org]

From: Ben Creisler
bh480@scn.org

Another new paper. Pdf is free.

Theagarten Lingham-Soliar (2010)
The evolution of the feather: Sinosauropteryx, a 
colourful tail. 
Journal of Ornithology 
DOI: 10.1007/s10336-010-0620-y  (advance online 
publication)  (Online First?)


A recent development in the identification of feathers in 
fossils by means of melanosomes was used to suggest that 
structures observed in an SEM of a filament in the basal 
theropod dinosaur, Sinosauropteryx, were phaeomelanosomes 
and that they represented conclusive evidence that the 
filaments were early feathers. At the most basic level, 
the claims of phaeomelanosomes are shown here to be 
founded on an optical illusion created when the SEM is 
reproduced at low image size?viewed at larger image size 
(~2× original) the structures are nondescript in both 
size and shape and impossible to equate with 
phaeomelanosomes. At a higher level of investigation, the 
study is seriously questioned for ignoring standard 
scientific protocol: despite size and shape being 
critical to the identification of the phaeomelanosomes, 
no statistically viable measurements of the structures 
(particles) were made?the measurements, which are simply 
conjectured, are shown here to be incorrect in the 
speculated sizes, and in shapes; inferences made on vital 
characters from birds and advanced non-avian dinosaurs, 
e.g. with respect to colour banding, are without 
confirmation in the test animal but conjectured on 
circular argumentation; alternative arguments, e.g. that 
the particles might be bacteria or colour from the 
overlying skin, are peremptorily dismissed or not 
considered; suggestions that the particles are embedded 
within the filament are without support since there is no 
evidence of cross-sections or tangential sections either 
made or occurring serendipitously?only a single section 
is reported, apparently of the filament?s surface. False 
dichotomies such as, if the structures are not bacteria 
they must be melanosomes, are questioned given that one 
of the most important factors in the taphonomy of ancient 
(structures in question, ~130 MYR) fossilised filaments 
i.e., decomposition?that the structures might reasonably 
represent the degraded remains of the filaments?is not 
even considered. Here, from experiments on the 
decomposition of native collagen in fish and reptilian 
dermis, SEMs of their ultrastructure show that 
distinctive spherical, elliptical or oblate particles, 
even more so than those figured in Sinosauropteryx, 
typically form during degradation. This is confirmed in 
SEMs of degraded collagen fibres in a 225-MYR ichthyosaur 
fossil, virtually point by point. In addition numerous 
small bead-like structures in the filament of 
Sinosauropteryx bear a striking resemblance to the unique 
67-nm D-bands of collagen, in both shape and size. This 
paper does not question the value of scientifically 
meritorious identifications of melanosomes, as indeed of 
collagen and keratin, in interpreting the integumental 
structures of fossil animals. However, allegations of 
phaeomelanosomes in Sinosauropteryx are shown to be 
without scientific merit. 

http://www.springerlink.com/content/4555m8h3x6035653/