Re: What feathers mean

[Jeff Poling <jpoling@dinosauria.com>]

At 04:17 PM 10/26/96 -0500, Lawrence Dunn wrote:

>Why do feathers on the newly discovered compsognathid equal 
>bird-ancestor?  Is it not possible that dinosaurs developed certain 
>features which paralleled those of birds?

   I'm not aware anybody *is* saying it's the most recent bird ancestor.
But theory has been that this type of dinosaur, compsognathids, shared a
common ancestor with birds, and the feathers strengthen THAT theory.

> [...] I heard one scientist declare that 
>Tyrannosaurs were cannibals because Sue's face was "torn off," 
>apparently, by another Tyrannosaur, and this is probably what killed her! 
> Does this equate?  Couldn't Sue have died and subsequently been 
>scavenged by another Tyrannosaur? 

   Again, I don't think you completely understand what you're reading.
Sue's face being "torn off" is merely ONE PIECE OF EVIDENCE among MANY.  As
with _Sinosauropteryx_ it strengthens a prexisting theory; in this case,
intraspecific combat among _Tyrannosaurus rex_.  Cannibalism is merely a
speculative extension of that.

>[Ouch.  I fear you're going to catch a bit of heat on this one.  First
> off, you've misunderstood the significance of Sinosauropteryx.
> People are excited about it because they think it's *not* a bird
> ancestor.  Parsimony would then suggest that other dinosaurs had
> feathers as well since the simplest scenario would be that feathers
> evolved before the most recent common ancestor of Aves and the
> Compsognathids.

   Mickey, I'm going to slightly disagree with you on this.  The cladogram
in my posession places _Compsognathus_ and _Sinosauropteryx_ as basal
coelurosaurians.  If _Sinosauropteryx_ is the hypothetical common ancestor
that denotes the clade, then it would, indeed be an ancestor of birds, just
not the most recent one.  It's a matter of degrees, which is damn hard to
keep straight sometimes....

[At 135 MA it seems a bit young to be what you claim, but you could be
 right.  -- MR ]

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