OT Cycads not ‘living fossils’

David Ehrlich idavide@sbcglobal.net
Thu, 24 Nov 2011 14:15:35 PST
From Science News  http://www.sciencenews.org/
Once thought to be the last remaining members of a plant lineage that went 
extinct with the dinosaurs, modern-day cycads are now believed to have diverged 
from a more recent common ancestor.
Although cycad populations suffered major losses about 65 million years ago when 
dinosaurs — their once primary dispersal agents — went extinct, the plants later 
experienced a renaissance due to a global climate shift, a new study suggests. 
Living cycads diverged from an ancestral species that flourished around 12 
million years ago, not from older dinosaur-era relatives, an international team 
of researchers reports online October 20 in Science.
To estimate the divergence time of living cycads, researchers used a technique 
called molecular clock analysis. First they measured the genetic differences 
separating 200 living cycad species. Since certain genetic changes typically 
accrue at a fixed rate once species radiate from a common ancestor, scientists 
were able to use this cycad DNA data, in conjunction with the fossil record, to 
predict a much more recent divergence. – Nick Bascom
My take -- one doesn't usually think of dinosaurs deftly plucking seeds from a 
cone to enjoy the fleshy aril; that's something a bird or small mammal might 
do.  I wonder what the cycads were like that depended upon dinosaur dispersal.
David E.
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