Re: Longisquama

["Matthew Bonnan" <mbonnan@hotmail.com>]

Dinogeorge said:
> We >always< need "better evidence" in paleontology. This is a triviality.
> What we really need to do is drop a few preconceived notions about what the
> common ancestor of birds and dinosaurs might have looked like, take a 
> better
> look at the evidence we already have, and see whether it leads to some
> interesting insights.

We always need better evidence: agreed.  But this observation has little to 
do with _Longisquama_ and consideration of a hypothesis in which this animal 
is ancestral to birds and dinos.  We need better evidence in the case of 
_Longisquama_ to better evaluate that particular hypothesized scenario.  Nor 
do I suggest that the present dino-bird hypothesis is somehow "true" or 
evaluated as well as it could be.  You're not suggesting that the scrappy 
Longi. specimen, neat as it is, is really the same sort of evidence as the 
Maniraptoran-bird hypothesis?  On the one hand, you have something which has 
not been shown to be either an archosaur or lepidosaur, on the other, 
definitive archosaurs which are similar in many respects to modern avians.  
Without going into all the possible homoplasies and homologies, I will argue 
that the Maniraptoran-bird hypothesis is much better supported at present 
than the Longi. hypothesis based on the evidence available.

Wanting better evidence in paleontology, or any science, is not a 
triviality.  There is nothing wrong with proposing that _Longisquama_ could 
have been an ancestor to birds and dinosaurs.  But I am not being trivial to 
expect to see what your evidence is for this hypothesis, nor am I being 
trivial in wanting better evidence than that currently available before I 
will consider abandoning the presently better supported Maniraptoran-bird 
hypthesis.  It is my job as a scientist, and in fact the job of anyone 
involved with science, to be skeptical.

I know you feel that the current dino-bird hypothesis is full of 
preconceived notions, and you may be correct.  I have to be open to that as 
well.  And perhaps the practitioners which developed the current scientific 
consensus in this case are jaded to new or contradictory evidence.  I give 
you that too, as I have to as a scientist.  But in science, whether or not 
the consensus hypothesis turns out in the long run to be falsified, anyone 
who challenges the consensus hypothesis must produce a hypothesis that both 
accounts for what was explained in the old hypothesis and also accounts for 
what the old hypothesis could not explain.

At present, it is not trivial to wait for better evidence concerning 
_Longisquama_ before rejecting or seriously questioning the current 
consensus hypothesis.  Evidence from multiple specimens, not one, framed the 
current dino-bird hypothesis.  Why should we reject this on the basis of 
evidence from one particularly poor specimen?

Matt Bonnan
Dept Biological Sciences
Northern Illinois University


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