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Re: Different take on BCF



Ron Orenstein wrote: 

>At 18:00 30/11/96 -0500, Tracy Ford wrote:
>
>> It is my gut feeling [stuff deleted -- MR ] it is the Enantiornithes
>> that are George's BCF and the theropods. The Ornithurae are a branch
>> from the Enantiornithes along with the 'Dino birds'.

Ron O. Repelied.

>While it is true that the Enantiornithines became extinct at the K-T
>boundary, they were not the earliest line of Mesozoic birds. In
>addition, they are not the only group of Mesozoic birds to disappear
>prior to or at the K-T .  Unless I am much mistaken, birds like
>Sinornis

Kurochkin has Sinornis as a primitive (sorry but I like to be 
politically incorrect) enantiornithine.

> or even Hesperornis are not considered to be enantiornithine.

Right, its an Ornithinae (or 'modern' bird). So, what's the problem?

>Thus it is incorrect to assume that the enantiornithine line is so
>similar to the basic stock from which birds evolved that it could be
>regarded as an ancestor to the so-called dino-birds - assuming that
>these creatures evolved from birds at all.

No, the problem is assuming that birds evloved along only one line.
Both Enantiornithine and Ornithiane birds are known from the Early
Cretaceous. Since both are known, there are two different lines of
birds in the Early Cretaceous. The line couldn't produce both birds
from only one line.  It's impossible.

Tracy