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feathers, hair and Compsognathus



Peter Buchholz wrote:

> Or, as I propose (maybe Greg does too), that pterosaur fur and
> Coelurosaur feathers (it feels so good to say "Coelurosaur
> feathers") are homologous structures and that all ornithodirans were
> furry (or feathered) at some point in their life.  One could
> theorise that feathers developed from fur because they were prettier
> or better insulators.  Who knows?

Actually there is no evidence that pterosaurs are furry (or to use the
correct term - pelage - as fur is a mammalian structure).  The only
evidence there is comes from Sordes pilosus and a Solnhofen specimen. 
Unwin and Bakhurina (1994 Nature 371 p.62-64) state that the pelage seen in
these specimens are, in fact, the fibres-stiffing rods that give strength
to the patagium (also the uro- and propatagiums).  So all you dino-art
people start painting/modeling them without!  I believe this work, as Dave
and Natasha were colleagues of mine at Bristol and I discussed this paper
in length with them - playing devils advocate with a role of total believer
of pelage and they convinced me (a particularly hard task - as you can see
by my scepticism of feathery dinos). 

> Any ideas as to why all known Compsignathid specimens died in the
> exact same pose?  That strikes me as very odd.  Also, how many
> fingers do you see?  Aside from the feathers, I think that the
> proper finger count will be the most important piece of evidence
> taken from Sinosauropteryx (how much do I hate that name?......).

I can't see the manus digits clearly as both limbs lie together and as I
said previously the fore limbs are slightly disarticulated making it even
more disarticulated.
The other question is easier to answer - Taphonomy - here is an excerpt
from that Archae taph paper I offered on the net

Pose of the Archaeopteryx skeletons:-
Heinroth (1923) used magpies (Pica pica) and pheasant coucals (Centropus
phasianinus) in experiments to investigate the 'bicycling pose' of the
Berlin Archaeopteryx ('bicycling pose' is my term for the pose that is seen
in all Archaeopteryx specimens (except the London and Maxburg) and
Compsognathus  - see Fig. 1).  Heinroth arranged fresh unplucked, plucked
and defleshed cadavers in the position of Archaeopteryx.  He ascertained
that after artificial detachment of the muscles and also some slight decay
the carcass adopted a position similar to Archaeopteryx.  He noted that,
after muscle tension has disappeared, the pull of the ligaments creates the
neck curvature as seen in Archaeopteryx.  Also in rigor mortis, the
antagonistic muscles all contract at the same time giving the same
appearance as in Archaeopteryx specimens.
        Moodie (1923) noted that Archaeopteryx, Compsognathus and some
pterosaurs exhibit a pronounced opisthotonos, "a tetanic spasm in which the
spine and extremities are bent with convexity forward, the body resting on
the head and heels" (Moodie, 1923, p.323).  He attributed such a spastic
spasm to the poisoning of the central nervous system by bacterial poisons,
mineral poisons or other toxins, which when liberated in the blood, attack
the brain and spinal cord.  This, however, is not believed to be correct. 
It is more likely to be due to desiccation as Heinroth (1923) assumed.
        Weigelt (1989/1927, p.105-106) argued that the curvature of the
neck (the backward bend placing the head above the centre of the back) in
the land/flying vertebrates from Solnhofen is a result of desiccation and
shortening of muscles and tendons after rigor mortis has finished.
        Rietschel (1976) indicated that wind-driven near-surface currents
operated from east to west which led to the transport of Archaeopteryx on
the water surface in an east to west direction.  He also suggested that
Archaeopteryx died by eating poisoned fish or invertebrates that were
washed up on the lagoon shoreline.  The dead Archaeopteryx then would have
floated for several days before sinking with the head and neck dorsally
bent.  He postulated that the head and neck would have come to rest in this
position on the sediment surface thus explaining this configuration in the
fossil specimens.
        To further ascertain the cause of the bicycling pose I repeated
Heinroth's basic experiment using a pigeon (Columba livra).  The pigeon was
defleshed by removing all soft tissues by dissection.  The pigeon was then
placed in a fume cupboard with the extraction unit switched on.  This
allowed a constant stream of air of room temperature (20 C) to pass over
the specimen.  The specimen was left for three days.  As in Heinroth's
(1923) experiment the neck curved backwards and the legs assumed the
'bicycling pose' evident in Archaeopteryx.  The carcass adopts this pose
because, without the muscles to act as an antagonistic force to the
desiccating and shortening tendons, the skeleton contorts into the
'bicycling pose'.  It is reasonable to assume that this same pose would
occur if the muscle tissue of Archaeopteryx had first decayed away
naturally before desiccation.  This experiment is not sufficient, however,
to indicate whether this desiccation was on land or due to being immersed
in the hypersaline lagoonal waters (i.e.. osmotic desiccation).

> Am I correct in my thinking that absolutely NO non-lepidosaurs have
> overlapping scales?  This is what you're advocating isn't it?  From
> the verbal discriptions I've heard so far, it seems far more likely
> that the structures are indeed feathers, and not overlapping
> Lepidosaur-style scales.  Also, all known dinosaurian scales are
> non-overlapping (there is a proper word for this right?), like
> Edmontosaurus, Carnotaurus et cetera.

Up to last week all reptiles were not feathered - yet you now believe this
to be untrue. So why not overlapping scales instead?  I was just indicating
until i have actually examined the specimen closely I am not prepared to
shout 'feathers' from the rooftops.  They don't appear to be feathers from
the PHOTOGRAPHS but the photos are not great!

regards
Paul
-----------------------------------------------
Dr. Paul G. Davis
Division of Vertebrate Palaeontology, National Science Museum, 3-23-1
Hyakunin-cho, Shinjuku-ku, Tokyo 169, Japan.
 
e-mail davis@kahaku.go.jp
Tel + 81 3 3364 2311
Fax. + 81 3 3364 7104
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