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Re: BFC Epiphany



On 9/26/07, Mike Taylor <mike@indexdata.com> wrote:
> Andreas Johansson writes:
>  > On 9/26/07, Mike Taylor <mike@indexdata.com> wrote:
>  > > Put this way, it's obvious that the problem is simply one of
>  > > characterisation.
>  >
>  > I don't think you can dismiss it like that. First, at least in that
>  > post, Olshevsky's topology is decidely unusual (monophyletic
>  > Phytodinosauria, Longisquama as a basal theropod).
>
> True, but I think that's a side issue
[snippage]
> Longisquama ... uh.  Not sure what's going on here: was George saying
> that it's more closely related to classic theropods than sauropods
> are?

Yes. From the very post you linked to: "it is likely that _Longisquama_ was a
dino-bird that had diverged from the central lineage after the phytodinosaurs".

Whether he's changed his views on _Longisquama_ and/or Phytodinosauria
since I do not know - I've only got his 1995 posts to go by.

>  If so, I dare say he's shifted position on that idea, too.
> Again, it's not close to the soul of BCF, it's just an incidental
> detail of one particular BCF-compliant model.
>
>  > Second, look at his summary of his hypothesis from a previous post
>  > in that thread:
>  >
>  > "The BCF thesis is that ALL dinosaurs--not just certain groups of
>  > theropods--were ultimately descended from small, arboreal
>  > archosaurs (which I call dino-birds), of which one lineage (which I
>  > call the "central lineage") represents an adaptive sequence that
>  > begins with a small, lizardlike, probably arboreal "ancestral
>  > archosaur" (perhaps resembling _Mesenosaurus_) and ends with any
>  > modern bird."
>  >
>  > That's more than a characterization of topology: it's a scenario of
>  > archosaur evolution. Whether we see Brachiosaurus brancai or Passer
>  > domesticus as the end goal of archosaur evolution is a matter of
>  > perspective: whether their last common ancestor was arboreal is
>  > not.
>
> OK, it's a fair cop -- I oversimplified.  Sort of.  But it's still
> true that this comes down to how you optimise the character
> transitions on your cladogram.  Given a matrix and a phylogeny, you
> can easily reconstruct the most parsimonious basal states.  Where
> George's model falls down is that the character states he advocates
> are grossly unparsimonious.

Exactly.

-- 
Andreas Johansson

Why can't you be a non-conformist just like everybody else?