K/T extinction probably global (was Re: K/T birds)

["Williams, Tim" <TiJaWi@agron.iastate.edu>]

John Bois wrote:


> I take issue with the bipolar division proposed for birds at the K/T.  
> Cracraft is saying that the bolide hit affected North Hemisphere and 
> that since neornithes were largely Gondwana species, and since the 
> Southern hemisphere wasn't hit as hard, they inherited the Earth 
>(rather than enantiornithes).  

The idea that the extraterrestrial impact 65 MYA had a "bipolar" effect on
the Earth's biota is undermined by:

Vajda et al. (2001).  Indication of a global deforestation at the
Cretaceous-Tertiary boundary by New Zealand fern spike.  _Science_ 294:
1700-1702.

Vajda et al. argue that the "Land of the Long White Cloud" was the "Land of
the Long Choking Ash Cloud" at the K/T boundary.  New Zealand shows a sudden
and stark decline in the diveristy of plant species at this time, similar
(though perhaps not quite as severe) as that observed in North America.  The
authors infer a combination of wildfires (which may have come first), a
prolonged winter, and acid rain, were to blame for NZ's dramatic change in
flora.  As the title implies, ferns (and ground mosses) were the winners;
gymnosperms and angiosperms (which disappear completely) were the big
losers.



Tim