Fwd: Aw: RE: Arboreal Theropods: The prize at the bottom of the cracker jack box

[Mike Keesey <keesey@gmail.com>]

On Tue, Jul 23, 2013 at 6:19 PM, Jason Brougham <jaseb@amnh.org> wrote:
>
> Some on this thread have mentioned that, if an animal is using trees in its 
> biology, it should show specializations.
>
> Recent work has found an ingenious way to test the time between a behavioral 
> shift and a clear morphological specialization.
>
> In fossil proboscideans that switched from a tree leaf diet to a grass diet 
> (as marked by carbon isotope ratios) the answer is 3 million years.
>
> I bet that is a long interval but, then again, tooth crown height should 
> increase faster (by shifting to the taller end of the pre-existing 
> distribution of tooth crown heights in the population) than complete descent 
> and reversal of a toe.
>
> http://www.nature.com/nature/journal/vaop/ncurrent/full/nature12275.html

That's really cool! But consider that basal eumaniraptors probably had
much shorter generation times (not to mention more offspring) than
proboscideans.

--
T. Michael Keesey
http://tmkeesey.net/