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Re: Pterosaur relationships

On Wed, 27 Sep 2000, David Marjanovic wrote:

> Maybe this topic should not be discussed on this list, but the current
> view of Ornithodira has become so entrenched that e. g. The
> Dinosauricon includes pterosaurs. My question is: What are, to date,
> the arguments for pterosaurs being close relatives of dinosaurs rather
> than Prolacertiformes?

Ornithodira is defined to include pterosaurs. The definition is something
like "the most recent common ancestor of Pterosauria and Dinosauria, plus
all of its descendants".

The widely held view is that this clade includes the two anchor taxa and a
handful of "lagosuchians". Under the alternate phylogeny (which I present
on my site in addition to the main cladogram) would include *many* other
groups (Pseudosuchia, Prolacertiformes, etc.), so many that I wonder if it
might not be a good idea to emend the above definition with a clause
specifically excluding Crocodylia (invalidating the clade under Peters'

That's just the taxonomic side of the issue. Hopefully some others can
discuss the actual character evidence.

T. Michael Keesey.........<tmk@dinosauricon.com>.........<keesey@bigfoot.com>
AIM <Ric Blayze>..............ICQ <77314901>...........Yahoo!M <Mighty Odinn>
Home Page (includes The Dinosauricon)........<http://dinosauricon.com/keesey>