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Re: Sinosauropteryx filament melanosomes challenged

Another fine paleontological contribution from the Journal of Ornithology.


12/5/2010 2:53 AM, John Hunt wrote:
No surprise there.  It amazes me how quickly bandits can knock out papers.

-----Original Message-----
From: bh480@scn.org [mailto:bh480@scn.org]
Sent: 04 December 2010 22:34
To: dinosaur@usc.edu
Subject: Sinosauropteryx filament melanosomes challenged

From: Ben Creisler

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.