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Re: More on Argentavis



--- Tim Williams <twilliams_alpha@hotmail.com>
schrieb:

> Michael Habib wrote:
> 
> >Granted, ostriches appear to be well above the
> maximum mass for a volant 
> >bird (though not the limit for volant vertebrates
> as a whole, see 
> >pterosaurs...), but many ratites are not.  Am I
> mistaken in saying that the 
> >evidence suggests an increase to ostrich size
> *after* loss of volancy, 
> >rather than a loss of flight in the specific
> lineage leading to ostriches 
> >as size reached maximum launch limits?

Ratites are a peculiar case, their flightlessness is
probably very highly convergent (based on place and
time of fossil record of paleognaths).

Essentially, ratites seem to be "big chicks", insofar
as that their morphotype seems at least partially due
to neoteny. That is, their acquiring flightlessness
was probably a more rapid process than in other
flightless birds which simply reduced the flight
apparatus.

The known flightless galliforms (a mere handful of
spp, all subrecent I think) on the other hand
generally became flightless due to size increase.

Eike


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