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RE: The extinction of small dinosaurs



--- Daniel Bensen <dbensen@bowdoin.edu> wrote:
> >>I can understand the effect of climate change, volcano activities and 
> asteroid hit etc causing the extinction of large sized dinosaurs but why
> it also caused extinction of smaller dinosaurs, typically like maniraptoran
> ??<<
> 
> It might help to define "small".  I remember hearing something like "all
> terrestrial animals over X kilograms were killed at the end-K", but I
> can't remember what the X was.
> 
> "Small" maniraptors like Troodon and Dromaeosaurus lived in Hell Creek
> right before the extinction, but those things were jackle-sized or
> bigger.  The size barrier may have been lower, like cat-sized and
> smaller, and it may have been that there just weren't any dinosaurs
> (aside from birds) that were that small at the time.  

Don't forget that most avian (sensu lato) clades went extinct, too:
_Enantiornithes_, _Hesperornithiformes_, _Ichthyornithiformes_ -- the *only*
surviving clade was _Lithornithiformes_ + _Neornithes_ (=_Aves_ sensu stricto).
Okay, _Hesperornithiformes_ doesn't count as small and terrestrial, but it
should not be forgotten that the K/T extinction appears to have wiped out
_Enantiornithes_ and _Ichthyornithiformes_, two clades of relatively small
maniraptoran dinosaurs.

=====
=====> T. Michael Keesey <keesey@bigfoot.com>
=====> The Dinosauricon <http://dinosauricon.com>
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=====> Instant Messenger <Ric Blayze>
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