Re: More on Argentavis

[David Marjanovic <david.marjanovic@gmx.at>]

Forwarded with permission, my comments added.

----- Original Message ----- 
From: "evelyn sobielski" <koreke77@yahoo.de>
To: <david.marjanovic@gmx.at>
Sent: Saturday, July 07, 2007 9:21 AM

> > >> and then entered Africa around the
> > >> Oligocene-Miocene boundary.
> > >
> > > Probably earlier, if _Struthio coppensi_ (or
> > > _Struthioolithus coppensi_) is good: Namibia, 20
> > > mya, osteologically rather "modern".
> >
> > The O-M boundary was 23.03 Ma ago...
>
> Yes, but there is an ample fossil record in Asia
> *later*. Ostrich egsshell is apparently autapomorphic
> in pore ontogeny, but it is not found in association
> with the Namibian bones which appear to show Struthio
> autapomorphies (description not seen).
> There are lots of ostrich bones & eggshell fragments
> with Struthio autapomorphies of ostriches in Asia
> later on.

Since when is there grassland in Namibia?

> > Synonymizing a taxon with an ootaxon from the
> > Miocene sounds like a bad
> > idea, BTW.
>
> No, it's different. As far as I get it, the ootaxon is
> a lapsus: eggshell was would with Struthio bones, but
> it's not Struthio eggshell. Apparently about the right
> size though. The only decent avian fossil record from
> sub-Saharan Africa is ostriches BTW.
>
> > *Palaeotis* lived in a paratropical rainforest. If
> > it was an ostrich
> > (...complete lack of cladistic analyses with a
> > serious sampling of fossil
> > ratites...), that means the ostriches must have
> > changed from forest birds to
> > grassland birds at some time. Perhaps that was the
> > Miocene/Pliocene when the
> > Eurasian grasslands developed.
>
> Hm, struthioniform, not ostrich.

I deliberately avoided the term "struthioniform" because it has been used in 
a number of meanings ranging from all ratites over rheas and ostriches to 
just ostriches.

> I'll check out the
> morphology of flightlessness of P. compared to
> Struthio (Now that might be interesting).

It is publishable. :-)

> In any case, it *seems* closer to the ostrich lineage
> than to any other birds. Its main significance is to
> gauge ostrich lineage basal vs ostrich lineage advanced
> among crown ratites.
>
> > ...complete lack of cladistic analyses with a
> > serious sampling of fossil
> > ratites...
>
> Indeed; a serious cladistic analysis (+ combined
> evidence) is sorely missing. I don't understand why
> the subject is being treated so piecemeal? It was
> technically possible to combine almost as much
> evidence 5 years ago as is available now.
>
> :(

It's simply hard, time-consuming work. That's usually the last thing that 
gets done.

But that has changed. Nowadays all that would be necessary would be to take 
the matrix by Livezey & Zusi and add taxa. (Adding yet more characters looks 
difficult.)