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Re: neoflightless dinosaurs



----- Original Message -----
From: "Nick Gardner" <n_gardner637@hotmail.com>
Sent: Sunday, September 29, 2002 7:19 AM

> >This is the sort of flight loss reversal thing that cladistics
> >is inherently hard pressed to handle.
>
> Why do you think cladistics are "inherently hard pressed to handle"
> reversals?

Without enough OTUs it certainly is. A good example is Ratitae. All known
ratites, dead or alive, are flightless. Therefore it's most parsimonious to
assume that they lost flight only once. Last summer or so, there was an
embryological study mentioned onlist which suggested that rheas had
descended from small fliers and ostriches from big fliers, arguing that
ratites lost flight at least twice. Biogeography, coupled with the latest
ratite phylogeny (still that from February 2001 in Nature), suggests that
this happened up to 6 times, unless the diversification of ratites happened
way back in the K. This discrepancy will likely stay unless we find a good
record of Paleogene ratites.

> >In fact, there is growing evidence that some short tailed flying birds
> >from the Jehol have strong oviraptor like features, which may
> >eventually show that the dinosaurs are descended from
> >birds more highly derived than even I suggested in DA.
>
> Your book was rather confusing (too many dashes and question marks, my
> head is still reeling from that) regarding this.  Could you please post a
more
> precise example (preferably in the form of a cladogram) onlist of what you
> were suggesting?

BTW, this is certainly feasible. In DA it says that it's still too early to
make a cladogram of theropods; while I agree that it is too early to do one
_and regard its results as definitive_, most if not all of the neoflightless
and post-Urvogel characters and their distributions are elaborated enough
that they could easily be fed into a character matrix.