Sinosauropteryx: not fuzz-less (long)

[dinoboygraphics@aol.com]

Jerry made some good points (for and against) the Lingham-Soliar et al 
paper, although he was more generous than I can manage after two 
readings of it.  I urge everyone to read the paper, but in brief:  
Lingham-Soliar (et al) examined a new(ish) specimen of Sinosauropteryx 
(IVPP V12415) under a conventional microscope, and argue that the 
preserved soft tissue morphology is consistent with collagen, hence 
presto-change-o there are no protofeathers on any Sinosauropteryx 
specimen.  Their own photos of specimen NIGP 127587 (figure 4a)  seem 
to indicate two very different tissue types, one with extensive 
parallel fibers that are almost certainly not epidermal insulation, and 
a dorsal surface that does resemble proto-feather epidermal structures 
as described in the type specimen of Sinosauropteryx (and other bird 
and feathered dromaeosaur specimens).  To explain this (and the 
proto-feather appearance of the type specimen) they postulate that this 
difference in morphology is due to "taphonomic degradation" of the 
collagenous tissuse, and cite the soft tissue preserved in the dorsal 
region of the neck of IVPP V12415 as representing an intermediate stage 
of decomposition (Fig. 2c), linking all of the preserved fiber types.

Their analysis is deeply flawed:

1) Despite David Marjanovic's assertation that Lingham-Soliar is an 
authority on collagen, little of that expertise is evident in this 
paper.  To begin with, they never actually provide a method (e.g. 
morphology, chemistry, etc) to distinguish fossil collagenous tissue 
from other fiberous tissues in vertebrate bodies (e.g. muscle and 
elastic tissues).  In particular, the tissue at the base of the neck of 
IVPP V12415 (figure 2c) is almost certainly not collagen.  They note 
themselves that the _straight_  parallel fibers seem to converge from 
the neck towards "a point".  That "point" is near the cervico-dorsal 
juncture, running from there to the posterior cervical vertebrae 
(http://skeletaldrawing.com/ext_photos/sinosauropteryx_stuff/fig2c.jpg). 
 This is an excellent match for the cervical musculature of birds, and 
is also not dissimilar to the elstic ligaments seen in ratites.  There 
are similar fibers running parallell between neural spines of the 
vertebrae (to clarify you can see the same image with photoshoped lines 
parallelling the fibers here: 
http://skeletaldrawing.com/ext_photos/sinosauropteryx_stuff/fig2c_fibers.jpg).

The fibers at the base of the neck not only resemble the neck muscles 
of birds in their location and orientation, they taphonomy practically 
demands that they be contractile or elastic fibers of some sort.  The 
fossil is in the classic death pose, with the neck dorsaflexed well 
beyond the normal life position.  This dorsaflexion pulls the neck back 
and shortens the tissues on the dorsal side of the vertebrae.  Collagen 
fibers are not elastic, and they don't "shrink" like muscles and 
elastic ligaments will; if those straight fibers were collagen the neck 
could not have ventroflexed back into life position!  Since collagen 
fibers are non-elastic, have tensile strength, but no comporessive 
strength a collagen frill on the dorsal margin could not be under 
tension with the neck pulled back.  Collagen fibers in this situation 
would look more like this:

http://skeletaldrawing.com/ext_photos/sinosauropteryx_stuff/collagen.gif

Since the fibers of the neck are all clearly shortening substantially 
to take up the slack created by the death pose, they have to either be 
elastic fibers or muscle fibers.  The latter seem more likely to me, in 
light their similarity to bird cervical musculature.   Lingham-Soliar 
do not even attempt to explain these problems, and appear oblivious to 
the fact that a dorsally located collagen frill should not exhibit 
linnear fibers while the neck is retracted.

In short, they are clearly correct that the cervical fibers in this 
specimen are not epidermal insulatory structures, but they fail to make 
the case that the fibers are collagenous, let alone dermal in nature.

2)  Establishing that the structures are either dermal or epidermal (or 
less superficial altogether), and either muscular, elastic, or 
collagenous is problematic on all the fibers preserved in IVPP V12415.  
Similar arguments apply to the tail (Fig 2 a & b); in particular, the 
supposed tail "frill" section with a solid dorsal margin exhibits a 
more gradual curve than the neural spines that it would overlay, 
looking more like taught tissue that has partially pulled away from the 
tail as it contracted, rather than a feature that extends the entire 
length of the tail (you can actually see it disapearing distalling the 
figure 1a).  The taphonomy is consistent with this, as while assuming 
the death pose the main portion of the tail has actually pulled away 
from the tail tip and an otherwise articulated portion of chevrons.  
There was clearly enough connective tissue/musclature to hold portions 
together and pull the tail into the death position, but decay was also 
advanced enough that the caudal vertebrae were ripped away (while 
remaining otherwise articulated) from the chevrons and tail tip, which 
themselves remain in articulation.  To claim that these fibers (which 
look different from the type specimen) are homologous with the 
structures seen in other specimens without the type of detailed 
comparison that the authors' themselves decry in other studies(!) is 
beyond careless: it's special pleading.

3) Taphonomy... speaking of special pleading...  The paper attacks 
previous authors for ignoring the roll of taphonomy, and 
then...completely ignores the taphonomy of their specimens!  For 
example, they repeatedly refer to the possible roll of wind and water 
"erosion" to play a roll in breaking down connective tissue into the 
appearance of insulatory structures, but don't even make a passing 
mention of the actual depositional environment of these specimens.  
Since current consensus is they are from low-energy fine-grained 
shallow lakebed sediments there is no evidence of significant water 
currents (it would take a lot to break down collagen) and wind seems 
unlikely underwater, to say the least.

4) They also show a photograph (Fig 4) of the tail of NIGP 127587.  
Despite claims in the paper, the photograph shows a dorsally located 
layer (apparently) consisting of dino-fuzz style insulatory structures, 
and a ventral layer of rigorously parallel non-epidermal fibers that 
are clearly not dino-fuzz (the taphonomy does not distinguish between 
collagen/elastin/muscle fiber hypotheses in this specimen like it does 
in IVPP P12415).  Unless it is a trick of the lighting, the photograph 
seems to indicate the epidermal/insulatory layer is preserved on a more 
superficial layer of rock than the collagen/muscles fibers are.  Worse 
yet, the proto-fuzz type fibers clearly extend down most of the way 
past the tail, indicating it is not a midline stucture.

5) Finally, the tone of the paper is inexcusible (to me).  Even 
ignoring the hypocrasy of chastizing previous studies for failure to 
consider taphonomy and do proper comparative work...while ignoring 
taphonomy (if not outright contradicting it) and failing to do detailed 
compartive work, the intro and conclusion is rife with phrases urging 
us to avoid "recourse to arbitrary conjectures on feather origins" 
(discussion section) that "strengthened the resolve of many 
palaeontologists that
birds are direct descendents of theropod dinosaurs." (introduction)  
This type of pejorative wording is distasteful enough on cable news 
shows; it has no place in scientific publications (well, perhaps in an 
editorial).

In summary, the paper spends a lot of time accusing other studies of 
the same flaws it commits.  The paper fails to make a good case that 
the fibers of IVPP V12415 are collagenous (especially the cervical 
tissues) or epidermal in nature.  It fails to link the fibers in IVPP 
V12415 to the proposed proto-feathers of the type specimen, and in fact 
presents a photograph that appears to contradict the idea.  They fail 
to provide a plausible mechanism that would decompose collagenous 
tissue into the appearance of insulatory strucutres, and the mechanisms 
they do postulate directly contradict the actual taphonomy of the 
specimens.

Hopefully this paper will be the stimulus for further research into the 
nature of the fibers preserved in Sinosauropteryx, feathered dinosaurs, 
mammals, etc. from Liaoning.  In the meantime, let's all strive to 
write more papers taht are more responsible than this one, regardless 
of conclusions.

Scott Hartman
Science Director
Wyoming Dinosaur Center
110 Carter Ranch Rd.
Thermopolis, WY 82443
(800) 455-3466 ext. 230
Cell: (307) 921-8333

www.skeletaldrawing.com

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