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Re: More on Argentavis



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.)