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Re: Island-dwelling dinosaurs (was Re: Gargantuavis neck vertebra)

Dr Ronald Orenstein <ron.orenstein@rogers.com> wrote:

> I was under the impression that the placentals-beat-marsupials argument had 
> been pretty well rejected, with evidence that the reverse may
>  have happened on Australia.

As far as Australia is concerned, this hinges on the identity of a
single molar, named _Tingamarra porterorum_, from the Eocene of
Australia.  The tooth has been regarded as coming from a "condylarth",
and therefore a non-volant eutherian.  If true, it indicates that
placentals were once established in Australia, but were beaten out by
marsupials.  However, not everyone is convinced that _Tingamarra_ is a
placental.  One suggestion is that the tooth comes from an
ameridelphian marsupial (also known from the Tingamarra fauna).  As
you might appreciate, this is a somewhat hotly contested topic.  ;-)