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Re: Fossil Discovery Threatens Theory of Birds' Evolution



In a message dated 6/24/00 1:09:43 PM, dbensen@gotnet.net writes:

<< That is a problem.  I say that a flightless bird _is_ a dinosaur, but other
people don't.  What we need is a diagnostic feature that we can find and say
"yes!  That's a dinosaur".  We can look at mammals' jawbones  (or teeth) and
seperate them from mammal-like reptiles, and that has made things much 
easier.>>

The defintion of "mammal" has changed in the last decade or so. How do you 
know that a live Olyagopolis would look like a reptile?  As to the former 
comment, I'm pretty sure that's right. Postosucius, has a theropod-like 
skull, but not a theropod-like body.

The problem is that you've got this thing sitting there. I remember my 
geometry teacher saying something to the effect that to prove something true, 
you need many logical and mathamatical steps, but to disprove it, all you 
need is a single equasion.

You've got all these elegant, logical and mathematical steps, and I've got 
the equasion.

<<Convergence is quite powerful, but it can only work with what it has.  
Dolphins
look a great deal like fish, but their tails move up/down not side/side 
because
the up/down movement is how mammals' spines move when they run.  If birds had 
not
evolved from dinosaurs, but from some crocodile-like ancestor, they would 
never
have displayed all of those dinosaur-like traits by mere convergence.  If
Longuisquama was quadripedal (which seems to be the consensus, although, to be
fair, the hindlimbs aren't there so we don't know), then it would have given 
rise
to a race of quadripedal birds.  Sound crazy, well quadripedal mammals gave 
rise
to quadripedal bats, didn't they?

Dan>>

Hey, life has gotten some pretty weird children. Look at spirula and 
graphitites, I know that neither is a vertibrate, but both evolved to look 
exactly like another group.

eric l.