Previously, we were joined with Lingham-Soliar (hereafter TLS) on the argument that the tissue structures in "dinobirds" were degraded collagen.
for a full accounting of this discussion.
Since the last time I posted on this topic, TLS has published a commentary
with G. Mayr on the topic of *Psittacosaurus* integument, but this story has
become a little more convoluted. For you see, TLS has not only published two
further papers on the subject of integumental structure, but two other papers
have also come out on the topic with the recovery of putative melanosomes in
Lingham-Soliar, T. & Plodowski, G. in press. The integument of Psittacosaurus
from Liaoning Province, China: Taphonomy, epidermal patterns and color of a
ceratopsian dinosaur. Naturwissenschaften Online Preprint, DOI
Abstract (it's a doozy):
"Preserved skin of small dinosaurs is rare. Here, a specimen of the
ceratopsian dinosaur, *Psittacosaurus,* presents some of the best preserved
epidermal scales observed to date in a relatively small dinosaur, over wide areas
extending from the head to the tail. We study the preserved epidermis of SMF R 4970,
the different types of scales, color, and patterns, and their respective locations
in the body. We use modern application of high-power digital imaging for close-up
analysis of the tubercles and fragments of preserved color. Three types of scales
are preserved, large plate-like scales, smaller polygonal scales or tubercles, and
round pebble-like scales. The sizes of the plate-like scales vary in different parts
of the body and vanish altogether posteriorly. Light and dark cryptic patterns are
created by the associations of the tubercle and plate-like scales, and there is also
evidence of countershading in the proximal caudal region, the body darker dorsally
ventrally. Perhaps most impressive are the distinctive pigmented impressions
of scales over most of the skeletal elements. The pigmentation follows the
curvature of the bones implying that when it was deposited, the skin was still
pliable and able to wrap around the visible parts of the elements. The present
record of color is the first in a non-theropod dinosaur and only the second
record in a non-avian dinosaur. Because of its resistance to degradation and
ability to produce various color tones from yellows to blacks, we suggest that
melanin was the dominant chemical involved in the coloration of
*Psittacosaurus.* The data here enable us to reconstruct the colors of
*Psittacosaurus* as predominantly black and amber/brown, in cryptic patterns,
somewhat dull, but useful to a prey animal. Indeed, skin pigment within a
partially degraded bone indicates that *Psittacosaurus* was scavenged shortly
after death. The theropod dinosaur *Sinosauropteryx* has recently been reported
o have naturally pigmented integumental structures, which th!
as proof that they are protofeathers and not support fibers of collagen. Our
findings in *Psittacosaurus,* on the other hand, indicate a more parsimonious and
less profound alternative explanation, i.e., decomposition of the skin releases
pigments that readily permeate underlying structures."
One of the more fascinating aspects of this paper is the specimen, the famous "quilled" *Psittacosaurus,* which
putatively incorporates detailed colors of patches of "skin" over various bones and between them. Just as fascinating is
the expression of constant naysaying about how this material is preserved. TLS & Plodowski refer to the structures of color and
scales as being "impressions," and leaving "traces" on the bones, but describe raised and detailed associations
of structures quite distinct from both bone and the meaning of the word "impression;" these are, in fact, the carbonized
remnants with their pigmentation intact of various integumental structures, as reported by the authors. How this doesn't apply to
*Sinosauropteryx* (the shape of the structures being different means that the structures preserved there must NOT be
supraintegumental, but subintegumental!
The authors even claim that their work represents the first case of widespread integumental preservation inferring color in Liaoning, referring otherwise only to *Sinosauropteryx* but restricting its color to the tail. The authors reflect briefly on the possibility that the colors they discern are natural, referring instead to circumstantial data (e.g., countershading) to imply their frequent use of the term "color" is parsimonious. However, the authors cite Zhang et al., 2010 on the appearance of "color" in *Sinosauropteryx* (more on this below), but do not reflect on recovering melanosomes in their detailed microscopic photographs. It seems an oversight on two fronts: Zhang et al studied more than just *Sinosauropteryx,* and that the detail of the microscopic study fails to investigate melanosomes (largely due to not utilizing SEM on this specimen).
A comment at the end of the paper (the last paragraph, in fact) bears
reiteration, as it extends from the discussion of apparently previously reported
discussion of color in fossils from Liaoning (disputed by TLS & Plodowski):
"Most recently, an SEM image on the theropod dinosaur, *Sinosauropteryx* (Zhang et al.
2010) from the Jehol biota purportedly shows the presence of melanosomes (see Lingham-Soliar and
Glab (2010) for an alternative explanation) in the integumental structures of the tail, which
the authors state is evidence that these structures were pigmented protofeathers and not support
fibers of collagen (e.g., Lingham-Soliar et al. 2007). Our findings in *Psittacosaurus* on the
other hand indicate a more parsimonious and less profound alternative explanation (accepting for
the present that the structures identified were indeed melanosomes)–pigment in the
integumental structures of *Sinosauropteryx* could easily have been absorbed from the overlying
decomposing skin, a phenomenon amply demonstrated in the present study in *Psittacosaurus* SMF R
4970, also from the Jehol biota."
You will all note (as I do) that some aspects of this paragraph are troubling. First, TLS
& Plodowski only mention *Sinosauropteryx*, while the study they cite also used
*Sinornithosaurus*, *Confuciusornis*, and an isolated "avian" feather. Structures
analyzed in that paper covered isolated areas of integument as well as regions overlying
bone. Second, the authors are willing to accept the existence of melanosomes in other fossil
specimens, and their relation to accurate preservation of supraintegumental structures, but
instead decide that they would rather interpret them as decomposed remnants of degraded skin,
overlying the subdermal collagen they have previously argued for.
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