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Re: K/T extinction (forams and birds)




Ken Kinman wrote:

     Forams were not wiped out.  Class Foraminiferea actually came through
K/T almost unscathed in terms of ordinal diversity.

It was my understanding that the forams suffered a profound crash at the end of the Cretaceous. Sure, they recovered (and went on to prosper, up to and including the present day). Many, many foramaniferan genera went extinct - the rest dribbled across the K/T boundary and spawned the multitude of forms that we see in the Cenozoic.


There is a hypothesis that the huge drop in forams was both product of and a contributor to the K/T extinction. These microorganisms pull vast quantities of CO2 out of the atmosphere to make their calcareous skeletons (calcium carbonate, or chalk). Any crash in their numbers may have caused rising levels of atmospheric CO2, leading to a greenhouse-type effect. After the nuclear winter caused by an extraterrestrial impact had passed, there may have come further ecological and atmospheric sequelae (both perhaps intertwined).


     As for Aves, the neornitheans probably just made it through by the
"skin of their beaks"

Most likely. Remember the canary in the cage, brought by the miners when they went "down t'pit"? If the canary karked it, it meant the air in the mines was unsafe - and time for the miners to leave.



Tim

------------------------------------------------------------

Timothy J. Williams

USDA/ARS Researcher
Agronomy Hall
Iowa State University
Ames IA 50014

Phone: 515 294 9233
Fax:   515 294 3163

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