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Patagium attachment Was: Re: Pterosaur.net



Dave, 

A quick response to your comments on my pictures:

My restoration of Darwinopterus does not show the tail incorportated
into the uropatagia: you can see that the tail does not broaden beyond
the posterior extent of the uropataigum as it would do if only the
dorsal portion were visible when incorporated into the membrane. My
other basal pterosaurs, aside from one or two very old restorations, do
not show the tail incorportated into the membrane, either. As for the
posture of the legs in the Darwinopterus image, the animal is meant to
be diving, swooping its wings back and narrowing the uropatagia to
lessen the wing area and minimise profile drag: why not use the legs as
extra control devices to alter the shape of the wings? Bats seem to do
it fine, so I'm sure we wouldn't see pterosaurs flapping around a set
leg posture. And what's so wrong with medial pointing fifth toes? With
the feet held in the position shown in the Darwinopterus image you only
have to flex the toes in 90 degrees from the pedal plane and voila:
medially pointing toes. There may be errors in the old Anurognathus
image you're pointing to, but the fifth pedal digit appears to be quite
opposable in basal pterosaurs and, if the limbs of such pterosaurs are
directed somewhat outwards during terrestrial locomotion (which,
according to Unwin 1988 and my personal observations of basal pterosaur
femora, they are), the toe doesn't have to wrap around the back of the
ankle that much. 

As for all the issues of bearing an unsplit uropatagium, I really don't
know what you're talking about: bats seem to reproduce and pass waste
just fine with a broad, unsplit membrane between their legs. The cloaca
was probably located beneath the membrane to avoid self-soling and, when
it came to reproduction, it's no problem for a the female pterosaur to
lift her leg up so the male can slide his cloaca next to hers or,
alternatively, for the male to posses a long penis that can help
navigate around a contracted membrane. Bats seem to copulate in the
traditional tetrapod fashion just fine, too: I can't see any of the
things you've brought up as being an issue.

Bottom line: the united uroapatagia of basal pterosaurs remains, in my
view, the best supported idea because of reasons discussed at length in
the pterosaur literature. I'm not going provide references or discuss
this further because, frankly, it's been raised enough on the DML and in
various other places. If you don't want to buy that evidence, fine, but
please stop telling the rest of us that our opinions are less valid than
yours because we don't agree with your views. Raising discussions and
questioning things is fine, but your tone is often more patronising and
arrogant than insightful. I don't mean this as a personal attack or
insult, but I'm sure I'm not the only DML resident who finds being told
that if we subscribe to your views that we'll finally 'work it out',
'see the light' or 'become one with nature' just a little annoying. Most
folks who reply to your posts do not take the same dismissive tone to
your ideas, so please show the rest of us the same respect.

Mark


--

Dr. Mark Witton

Palaeobiology Research Group
School of Earth and Environmental Sciences
University of Portsmouth
Burnaby Building
Burnaby Road
Portsmouth
PO1 3QL

Tel: (44)2392 842418
E-mail: Mark.Witton@port.ac.uk

>>> David Peters <davidpeters@att.net> 18/01/2010 13:37 >>>
M. Hanson wrote:
Lately I'm seeing claims made like this, and this quotation from the
Pterosaur.net site has piqued my interest:
"The more basal, paraphyletic âramphorhynchoidsâ had a broad
uropatagium that linked across the two hind limbs. By contrast, the
pterodactyloids had a uropatagium that was split, such that a roughly
triangular membrane ran along each hind limb [figure 3a]. The
uropatagium would have had several uses during flight."
This seems to imply that the uropatagium did not attach to the tail. I
am wonderin
g where the evidence for this comes from. It seems that the
only specimen that could potentially be interpreted as having a free
tail is the Sordes pilosus holotype, however, there is a peculiar fold
down the centre of the patagium that could be interpreted as the region
on which the tail originally attached, and due to decay it fell off. 

>>>>


For some reason a group of pterosaur experts have been applauding this
sort of nonsense lately (pterosaur.net; Unwin, 2004). Sad.
You're right, Mike. The uropatagia were split, as in Sharovipteryx and
Pterodactylus [phylogenetic bracketing tells us that if not good ole
observation].

Dr. Witton has an interesting take on this:

http://www.flickr.com/photos/markwitton/4010200611/in/set-72057594082038974/


a bit of both worlds here. Uropatagia attached to the tail, but narrow
span wise, so much so that the elongated fifth toe is attached at its
tips only millimeters from the tail. Don't try to walk in this
configuration! Suggestion for Mark, extend the hind limbs out like
horizontal stabilizers on a small airplane. Add more meat to those
thighs to match the extent of the ilia. Remove pedal digit V from any
interaction with the uropatagia. Remember Tanystropheus,
Langobardisaurus and Cosesaurus have a homologous digit V and they
didn't fly. No pterosaurs preserve the uropatagia in association with
digit V.  Digit V is commonly found folded upon itself, which ruins any
membrane that can be imagined there. Finally, when you extend the hind
limbs quite a bit laterally, there's another bad situation that develops
with regard to attaching the brachiopatagia at the ankles, so follow
John Conway's model, and the example of every known brachiopatagium in
the fossil record and attach the big wing proximally at the anterior
mid-thigh. Suddenly everything will make sense and you'll be One with
Nature.

In contrast with the preceding example, here Dr. Witton goes the other
way and attaches the uropatagia to each other:

http://www.flickr.com/photos/markwitton/149392935/in/set-72057594082038974/


with digits V pointing medially (ouch) and framing the uropatagium
trailing edge. I've always wondered in this configuration where the
cloaca emptied. If above the uropatagium, then the poor thing is
constantly soiling itself and to get rid of the accumulated guano, must
clean itself like a contortionist. If below the uropatagium, then
there's no traditional tetrapod sex. They will have to "do it" bonobo
style. 

Best to just split the uropatagia. It solves so many problems! Shift
that paradigm!!!

David Peters

 (additional queries answered below)


Also, I am interested in how the long bony struts in the final caudal
vertebra of Pteranodon is interpreted if the tail is unattached.
Additionally, what would be the aÃrodynamic implications of a free
tail?


>>>>

No uropatagia are preserved with Pteranodon. Considering the fragility
of those tail bones, I would guess they were unencumbered. 

Minor if small. Less minor if elongated. The tail vane, while
decorative, would have acted like arrow vanes in keeping the tail
aligned with the direction of flight.