[Taxacom] Poor flying hoatzins dispersed (in flotsam)

[Michael Heads]

Hi Ken,
?
Yes, a unique event is rare, but... An event that happens once every thousand years - say a tsunami travelling from A to B - is very rare in ecological terms and is the sort of thing often invoked in?chance dispersal theory. But in geological time such an event?is very common - there would have been 65000?since the Cretaceous and so they don't really explain a group comprising?just one clade in A and one in B (such as the hoatzins in America and their fossil in Africa). That requires? a unique event.???
?
Michael

Wellington, New Zealand.


My papers on biogeography are at: http://tiny.cc/RiUE0


________________________________
From: Kenneth Kinman <kennethkinman at webtv.net>
To: taxacom at mailman.nhm.ku.edu
Sent: Thursday, 13 October 2011 4:42 AM
Subject: Re: [Taxacom] Poor flying hoatzins dispersed (in flotsam)

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? ? ? ? ? ? ? ? ? ? 
------------------------------------------------------
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 




_______________________________________________

Taxacom Mailing List
Taxacom at mailman.nhm.ku.edu
http://mailman.nhm.ku.edu/mailman/listinfo/taxacom

The Taxacom archive going back to 1992 may be searched with either of these methods:

(1) by visiting http://taxacom.markmail.org

(2) a Google search specified as:? site:mailman.nhm.ku.edu/pipermail/taxacom? your search terms here