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Re: The Papers That Ate Cincinnati + teeth



--- "T. Michael Keesey" <keesey@gmail.com> schrieb:

> On 5/5/07, Tim Williams
> <twilliams_alpha@hotmail.com> wrote:
> >
> > A stem clade "Panopisthocomiformes" could be
> erected for all birds closer to
> > the hoatzin (_Opisthocomus hoazin_) than to any
> other modern bird.  It might
> > include such fossil taxa as _Hoazinoides_ and
> _Foro (if not a
> > musophagiform), though probably not the highly
> dubious _Onychopteryx_.
> 
> Presumably the panclade name would be
> _Pan-Opisthocomus_ or
> pan-Opisthocomus or something along those lines. It
> would be
> permissible, e.g., to define _Opisthocomus_ as
> "_Opisthocomus hoazin_
> and all of its descendants". (Although I've never
> seen anyone propose
> a definition like that, it would yield a crown clade
> with the same
> currently extant content as the species.)
> 
> Or we could simply leave it unnamed for now and
> refer to the total
> group of hoatzins or stem hoatzins or whatever.
> 
> Alternately, you could use _Opisthocomiformes_ for
> the total group.
> 
> > The alternative is to make Opisthocomiformes
> apomorphy-based,
> > as Clarke et al. (2003) suggested for
> Sphenisciformes.
> 
> Not a bad idea, either. (With the character of
> manual unguals in
> juveniles, perhaps? Or digestion by fermentation in
> the crop?)

I'd rather go with a stem-based definition as per
above. Nothing is known about the evolution of these
apomorphies in the Hoatzin, and the first one is of
dubious value (the genetic basis is likely not too
complex)


Regarding apomorphies: is there a good modern theory
on the evolution of the hesperornitine teeth? (I
*think* their ontogeny and morphology is unique, at
least Marsh's "Odontolcae" seems to imply this. Let's
hope for a _Gansus_ skull to turn up!)


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