RE: The mystery of the furcula

["Williams, Tim" <TiJaWi@agron.iastate.edu>]

George wrote:
 
>The furcula carries a lot of weight in theropod systematics, 

Who says?

You're making a bold assumption here, which you can't possibly back up.
Heck, ornithologists to this day are still debating what the furcula is
actually used for.  And even if someone is absolutely certain what it is
used for in birds, it doesn't automatically tell you what the original
function of the furcula was.  

The furcula (fused clavicles) is found in some theropods and not others, and
even _Longisquama_ has something that looks like a furcula.  And if you're
going to tell me that a furcula is an essential component of flight, then
I'll point you in the direction of a few parrots that lack one.  They fly
very well too.


Tracy Ford wrote:

>> But it illustrates the point that we shouldn't pick and choose our 
>characters - unless we have damn good evidence 
>that they're developmentally or functionally linked.<< 

>But this happens all the TIME! 

I meant (and I think my post made this very clear) that I was referring to
the subjective culling of character sets.  In other words, "The distribution
of this character is screwing up my pre-conceived phylogeny.  So out it
goes!"  E.g. George thinks that the furcula is of paramount importance in
theropod phylogeny: but his cladograms are not telling him this, he is
telling his cladograms.


And back to sauropods...

>NO, no, no. This assumes that all sauropods ARE titanosaurs and they go
>from there.  Nemgetosaurs are Diplodocids, Brachiosaurs are Brachosaurs, 
>Opisthocoelicauda is a Camarasaurid, and Titanosaurs are Titanosaurs. 
>Nature is very diverse and people need to understand that and not have 
>tunnel vision with cladagrams. 

I stated that the vast majority of LK sauropods belong to a monophyletic
group, the Titanosauriformes.  This embraces a great deal of diversity.
Chopping this clade up into smaller "families" in another context doesn't
alter this one iota.  Similarly, discussing tyrannosaurids, dromaeosaurids,
birds and therizinosaurids under the umbrella of "Maniraptorifomes" doesn't
deny the diversity of this group.  


> >Then we're back to birds evolving from megalancosaurids, simply 
> >because "my sixth sense tells me" that long arms and a triangular 
> >skull of _Megalancosaurus_ carry more weight than the 135 characters 
> >that place Aves within the Theropoda. 
> >Certainly, this is an extreme example (and I'm not accusing George of 
> >subscribing to such nonsense). << 

> Kind of sounds like it though. 

It wasn't my intention.  I'm familiar enough with BCF to know it doesn't
posit a drepanosaurid origin for birds.  



Tim