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re: Tanystropheus neck posture



Maybe Tanystropheus wasn't marine.

I just took a look at Wild 1973 and note that in exemplar q, the most
complete Tanystropheus published therein, the joint between dorsals 1
and 2 is angled about 40 degrees. Other nearby joints have lesser angles
between verts. To my eye there is no neck contraction, but rather it
appears to have a camarasaur-like setup.

Just a wild hypothesis, but what if Tanystropheus fed on arboreal
diapsids, like longisquamids and basal pterosaurs, by standing at the
base of trees and searching the boughs for prey?  The clincher is the
giant penile bones would make great bases for a tripodal posture.

David Peters






>>Just a short note, Tracy.

>>I for one do not know how Tanystropheus swum, but  I am not that sure
that
the posture of the skeleton in fig 4 at p.15 (which represent a finding
"as
preserved"), represents also a swimming  posture as suggested again at
p.22.  To my eyes it represents a taphonomic condition of post mortem
contraction of neck muscles/ligaments, as you can see in many long
necked
vertebrates.<<

>This is a problem to say the least. But from my understanding of how
post
mortem works is the animal has to dry out. The skeleton has be left out
to
dry so the contracting muscles/ligaments can pull the neck/tail back. As
can
be seen in many wonderfully extant and extinct animals. BUT, these are
from
an aquatic environment (ocean floor) and I don't know how the animals
could
dry out so post mortem can set in. If anyone can point me to references
that
explain how that can happen would be great.<

>>First, I suppose you refer to the Tanystropheus specimens from the
Anisian/Ladinian Grenzbitumenzone/Besano Formation of Italy and
Switzerland.
They did not deposit on the ocean floor. They deposited at the bottom of
a
relatively deep (or relatively shallow, it depends on your point of
view)
marine basin, but not an oceanic one (neither in the geological nor in
the
geographical meaning of the word "oceanic"). Tany is associated with the

rauisuchian Ticinosuchus and the prolacertiform Macrocnemus, that were
terrestrial animals (at least the first).<<

Ok, I should have said marine, but it still in an aquatic environement.
Ticinosuchus was probably a bloat and float, and Macrocnemus?
Hmmm...naris
dorsally placed, hmmm....yea I've thought of that one also...

>>Second, maceration in hypersaline solutions or hot water could also
produce
the typical arching of dried carcasses. I do not have direct experience
of
that, I read it somewhere, I do not remember where. Also floating causes
an
arching of the carcass (see Schaefer, 1972).<<

Do you remember which publication so I can narrow it down more? Thanks.

<<Now, if I'm correct and it is a snap shot of how the animal moved,
then
the
animal would have had to have died in the position (which I can't
explain).
IF the animal sank to the bottom then somehow moved into that position,
would there be ripples in the mud to show that the animal did move?
Don't
know.>>

>>Currents are always present, also in closed, oxygen-depleted basins.
Water
is never completely still. Ripples form easily in sand, but it is much
more
difficult to form them in mud, because it is more cohesive (i.e., grains
do
not move). Thus, the absence of ripples in the muddy bottom of the
S.Giorgio/Besano basin does not mean that weak current were absent.<<

Thanks.

Cheers,
Fabio
------------------------------

Fabio M. Dalla Vecchia, PhD
Museo Paleontologico Cittadino
Via Valentinis 134
I-34074 Monfalcone
ITALY
http://www.fante.speleo.it



Tracy L. Ford
P. O. Box 1171
Poway Ca  92074