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Re: Sharovipteryx an ornithodiran??




"Jaime A. Headden" wrote:

> David Peters (davidrpeters@earthlink.net) wrote:
>
> <Sure finger V of pteros is tiny, but that goes back to Macrocnemus. In fact
> the relationship of IV to V is always much greater in every member of the
> Macrocnemus > pterosaur clade than in any archosauriform.>
>
>   I would like to remind debators that in this case, one must use evidence 
> that
> can be verified or has been verified in making one's arguments or corollaries.

Go get the opposing evidence:  My evidence is on the website: pterosaurinfo.com.
and it shows up, or will show up in  Prehistoric Times. And speaking of 
evidence,
even when the evidence is as big as a big dang sauropod cervical, there's still
some wiggle room apparently. So remember, when we argue, evidence doesn't solve
problems and bring warring parties together.

And that's O-K!



>
> The technique Dave has used to reconstruct ptrerosaurs, pterosaur ancestors,
> and his subsequent phylogeny, has been questioned without a clear modus
> presented on precisely using the technique used to do so. Thus we should
> attempt to corroborate our data without it until it is proven.

So much bs Jaime. Quit pontificating and start laying out the prosecution. The
best way to bring me down would be to bring evidence to the contrary.


>
>
>   Similarly, arguing about "pterosauromorphs" being crocs from an abstract is
> not the same as examining the material, or at least reading the dissertation
> itself, which I highly recommend.

I  can take apart the evidence written in the abstract point by point and I have
done so in correpsondence with the author. If you want to bring it out in the 
open
bring the abstract in question to the forum.

>
>
>   Statements requiring at least some amounts of assumption, such as "that goes
> back to Macrocnemus", in that it implies a relationship of direct comparisons,
> should be elaborated if they are to be held in contention to the prevailing
> theory, which does not support prolacertiforms in this case as pterosaur 
> allies
> (not that it really supports anything else right now save for a few large
> cladistic analyses which have been verified and some general phyletic
> comparisons).

It's been five years since that Macrocnemus > pterosaurs theory hit the presses.
No one has dented it yet. No one has called it into question. They all give it a
tip of the hat, or tiptoe around it like the elephant in the living room. Case 
in
point: David Unwin's pterosaur book. If there is anything wrong with the
macrocnemus hypothesis, someone would have pointed out a flaw by now. You know I
would have. Or if PAUP had found a better match, someone would have alerted us 
by
now. PAUP nests everything. Even a second cousin will do. And, at present, this 
is
best nesting.

>
>
>   Anyways, I have not much to say on the matter of *Sharovipteryx*, given how
> poorly it is poreserved,

More bs. It is wonderfully preserved. Skin and bones. Few fossils are as
wonderfully preserved.

>

> he difficulty of discerning much of anything about
> the region anterior to the shoulders, and the details of the skull at all.

More bs. The skull is complete. The pec girdles are there. The problem may be in
the amount of skin still present obscuring certain features. And, of course the
big cracks in the matrix. Plus, name one person, other than Sharov, who has
published detailed drawings of the critter. It's no picnic, but it can be done.

> The
> arms are incomplete,

More bs. And I'm not the only one who has seen the arms now. Two others I know 
of
in separate hemispheres.


> and I do not agree with Dave's interpretation of long
> arms, given the remains are also partially disarticulated and thus,
> untrustworthy regarding consistency of form.

More bs. The remains are completely articulated. Just crushed.


> In *Scleromochlus*, I have said
> plenty before, and I largely agree with Benton in placing it close to the
> archosaur root, but like Dave, I do also see a lot of croc-like features.
> Unlike Dave, I caution myself that many of these seem plesiomorphic, and would
> exist even in basal dinosauriforms deriving from a croc-like basal archosaur
> which gave rise to both crocs and dinosaurs. When looking at taxa closer to
> dinosaurs than *Scleromochlus* has been proposed to, we see many of these same
> features. In fact, *Scleromochlus* shows them in even further reduced form, 
> and
> appears to be more dinosaurian in the structure of its pes, metatarsal
> arrangement, fifth toe, and proximal tarsals, than does even *Lagerpeton* or
> *Marasuchus*. That said, there are also some crocs, such as the possibly
> paraphyletic grade of taxa called "sphenosuchians", that have developed some 
> of
> these features as well, and we should be concerned over how we interpret
> possible convergences. And that goes for anyone proposing a feature is
> indicative of some phylogenetic lineage or another, any lineage, and any
> researcher. Convergences happen, deal with it.

Lots of agreement here. See, it's not just a bad mood. But basing a nesting on a
few key features is dangerous. Take 150 to 225 characters and then feel safe 
about
a nesting.

>
>
>   Cheers,
>
> Jaime A. Headden

And more cheers.

David Peters
St. Louis