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multi questions re: pteros
Jaime Headden wrote:
David Peters (firstname.lastname@example.org) wrote:
<And in pteros, even a raw tracing is an interpretation. You have to
Best with the specimen itself, and if you have to rely on anything
from that specimen in person, very high quality and detailed photographs
of the specimen, with sets of photos of the parts of it. This reduces
interpretation a good deal. Otherwise, a skeletal drawing can be of
use for coding purposes than a camera lucida drawing, or other form of
DP: Best if you hoard all the specimens in your cabinets and examine
each one over the course of a year or two as questions arise. 2nd best,
if you examine the specimens, take your photos, trace them on the best
medium possible with the finest pencil possible (and I'm talking about a
computer scan) --- then double check your findings with the specimens
again in a whirlwind dash around the globe.
In the meantime, if I can get a Scaphognathus nostril to extend over
twice my monitor, I'm pretty sure of what I'm seeing. Then, if the
cladogram says other specimens show the same character, then I feel even
more certain. Then, if the reconstruction doesn't look like an Ed
"Big Daddy" Roth drawing of Drag Hag, we might have something.
Still, worth testing with a race around the world though. That'll
<And that's what I'm offering.>
Then we can wait until they do? Or we do?
DP: I think I was offering to help certain workers see things from an
alternate perspective with jpeg evidence. Not sure what the questions
refer back to. What do you need? I'm here for you.
<dp: It surprised me also the variety of sizes in pterosaur fingers and
toes. It's codable.>
But this doesn't answer my question about relative displacement.
Yes, there are lots of cases of displacement, disarticulation, bone over
bone and everything else. Even "soft" unossified fingers have been
identified. That's why it has taken so long to work it all out, and then
to write it all out. Every character in over 100 specimens has to be
right, 177 times (that's 17,700 matrix boxes to fill without error). I'm
working on the text now.
David Marjanovic wrote:
> DP: Would a few examples be enough to illustrate the chimaera problem?
One can code polymorphisms. :-) This lets PAUP* sort out which of the 2
more states is plesiomorphic within the group, as if its species were
separately, but still keeps the matrix small.
DP; True. But none of Unwin's matrix boxes were coded for that, as I
> If you have more than one tree in the end, as in Unwin 2003, there's
something wrong, you didn't dig deep enough, because in nature there is
Eh, but there's no possibility to tell _what_'s wrong. Because that
the sampling of the fossil record. It doesn't have to be the coding.
(Extreme example -- put *Alexornis* in any matrix of basal birds, and
come out in a polytomy, because it consists mostly of missing data.)
DP: I found what was wrong dozens of times in pterosaurs and came up
with a single tree in the end. PAUP can be very helpful. Some taxa are
headless. Some are bodyless. Fortunately there is just enough data, like
I said, a critical mass. Love to have more. Don't have more.
I can't comment on birds. Don't know.
BTW, here's the list of things you can see on pterosaurs that are not in
1. Finger five.
2. Wing finger ungual.
3. Jugal extending to nostril.
4. Secondary nostril (appears in a variety of scaphognathids prior to
the dissolution of the primary ascending process of the maxilla and
afterwards can be found in their descendents by tracing the nasal and
jugal forward, beyond previous interpretations, to midway down the
rostrum. Beware though, in ornithocheirids this area is sometimes
damaged and preparators have filled the hole with putty because it's not
supposed to be there. In others there may be medial sheeth of bone that
blocks the matrix from showing through, but the depression will be
there. Ctenochasmatids and Azhdarchids, because they are derived from
dorygnathids, do not lose their original naris. It's just hard to see,
but it's there.
5. Toe five ungual on five or six of the most primitive pterosaurs. This
does disappear finally.
6. Extended caudals,many with tassel tips and vanes.
And lots of other, reportedy missing, bits and pieces, different on each
taxa. Check em out.
Impressions and stains are real.