[Taxacom] Poor flying hoatzins dispersed (in flotsam)

[Kenneth Kinman]

Dear All, 
     Well, I guess I am butting my head up against a Kiwi brick wall, so
won't waste much more time on it.  Anyway, it seems to me that unique
events are automatically rare (by definition), so that argument seems a
semantic distinction of little or no importance to this discussion.  And
besides, we don't know for sure that all such transoceanic dispersals
are actually unique.  Nile crocodiles could have dispersed across the
Atlantic to South America on two or three different occasions for all we
know.  Arguing semantics about unique vs. rare just deflects attention
from more important issues.       

        And I certainly agree that "many taxa survived the end of the
Cretaceous and leave their biogeographic mark in the present."  I just
don't think hoatzins would have survived, EVEN IF they were present in
the Cretaceous.  And frankly, I seriously doubt that they evolved that
early or even in the Paleocene.  I wouldn't be surprised if they evolved
in Africa during the Eocene or Lower Oligocene, and thus that is where I
would tend to look for the mother (and sister) groups of Order
Opisthocomiformes.  But if someone wants to look for hoatzin fossils in
the Cretaceous, I wish them good luck (but I obviously won't be holding
my breath since that seems more of a fantasy to me than a Cenozoic
transoceanic dispersal event).          
           ---------Ken Kinman                     
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John Grehan wrote:  
      Heads has already commented on the nature of these imagined
dispersal events being unique rather than rare. As for surviving the
Cretaceous extinction, 'specialized' or not, the spatial correlation of
distributions and tectonics does indeed suggest that many taxa survived
the end of the Cretaceous and leave their biogeographic mark in the
present. 
John Grehan