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Re: More pterosaur phylogeny - I AM NOT A WUSSIE!!!



----- Original Message -----
From: <h0662eka@rz.hu-berlin.de>
To: <dinosaur@usc.edu>
Sent: Tuesday, November 25, 2003 6:10 AM
Subject: More pterosaur phylogeny - but not for wussies!


> Pterosaur phylogeny....
>
> > Yes, I agree completely with Chris, probably the most important
difference
> between Unwin 2003 and Kellner 2003 is the distribution of character
states
> concerning the notarium. However, if one compares our preferred cladograms
> carefully you find that the two distributions involve relatively few
changes. To
> get from my preferred cladogram to Kellner's you only need to lump
> Ornithocheiroidea into a single clade with Dsungaripteroidea and
Azhdarchoidea
> (as I conceive them) and leave Ctenochasmatoidea (=
Archaeopterodactyloidea of
> Kellner) outside this clade. Then pull out Germanodactylus from
> Dsungaripteroidea, force it into Ctenochasmatoidea and thats about it -
you can
> get from Unwin to Kellner in a few easy steps.
>
> Be that as it may, there are other problems with the clade supported by
notarium
> characters. So far as I understand it, Tapejara does not have a notarium,
> although it is deeply nested within this clade and basal to other
azhdarchoids.
> And, so far as I can tell, Haopterus, which seems to be a basal
ornithocheiroid,
> also lacks a notarium. Note also that these taxa are represented by
relatively
> small or medium sized forms - which fits with my explanation of the
appearance of
> the notarium as size related.
>
> That said, I happily accept that the distribution and definition of
notarium
> characters and the clade(s) they support are still major issues and need a
lot
> more study. But, I'll stick my neck out and bet a bottle of champagne
(with the
> first person to take up the challenge by emailing me directly -
> david.unwin@rz.hu-berlin.de), that ultimately this structure will prove to
be
> homoplastic within Pterodactyloidea.
>
> Any takers? Or are you all wussies!
>

I'll gladly take your bottle of champagne, however, we may be talking apples
and oranges here.  I have been aware of this for quite some time, but have
not taken the time to clarify the situation.  You are talking about the
notarium while I was talking about the advanced pectoral girdle.  To me a
notarium is simply a series of coossified anterior dorsal vertebrae, and it
is certainly conceivable that such a structure could have been evolved
convergently in various lineages of pterosaurs, just as notaria have been
eveolved in various birds, and the fossil record of small pterosaurs may not
be adequate to determine in all cases whether the anterior dorsal vertebrae
were fused in fully mature individuals.  For example, do we know whether
Gnnathosaurus had its anterior dorsal fused into a notarium?  No, all we
know of its poscranial skeleton is based on immature individuals that have
been called "Pterodactylus micronyx" in the past.  When I talk about the
advanced pectoral girdle of large pterodactyloids, I am talking about the
complex of osteological characters that includes a scapulocoracoid with the
scapula rotated so that it articulates with the supraneural plate of the
notarium in the region of the 3rd and 4th dorsals, and with anterior dorsal
ribs fused to the the notarium, AND if you read my contribution to the
pterosaur symposium volume that complex of osteological characters reflects
a whole series of changes to the pectoral musculature as well.  I have not
suggested that the mere presence of a notarium is a synapomorphy of a
Dsungaripteroidea as the term is used by Kellner and myself, however, I do
think that the complex of characters that I term the advanced pectoral
girdle is a synapomorphy of such a clade.  SO, if you are willing to tie the
champagne to the advanced pectoral girdle rather than a notarium, then I'll
consider it a wager.

Chris


S. Christopher "NOT A WUSSIE!" Bennett, Ph.D.
Assistant Professor of Basic Sciences
College of Chiropractic
University of Bridgeport
Bridgeport, CT  06601
http://www.bridgeport.edu/~cbennett

"Savor the sun--but when the clouds come make animals"  (Hexum)