Re: New dinosaur diversity articles

[Tim Donovan <uwrk2@yahoo.com>]

--- Mike Taylor <mike@indexdata.com> wrote:
> > 
> >   Lambeosaurs appear far less diverse in North
> America by the early
> > Maastrichtian. Hypacrosaurus is the only post
> Campanian NA
> > lambeosaur genus known AFAIK.  Centrosaurines were
> also down to one
> > genus by then-Pachyrhinosaurus-and were totally
> gone by the late
> > Maastrichtian. Saurolophines had also vanished by
> then. The recent
> > Ankylosaurus paper claimed that ankylosaurs
> disappeared before the
> > end. That may not have been true of Ankylosaurus,
> since specimens
> > are stratigraphically high, and one occurs right
> below the K-T
> > according to Wroblewski's data. Edmontonia,
> however, may have
> > disappeared before the end.
> 
> Isn't this just a matter of lambeosaurines being
> superseded by
> hadrosaurines, centrosaurines by chasmosaurines, and
> nodosaurids by
> ankylosaurids?


 The point is that diversity did decline prior to the
end, indicating that other factors* were at work
causing extinction. Btw, I don't think the
hadrosaurines and chasmosaurines etc eclipsed the
other taxa, they just proved less vulnerable in the
face of something else. Someone suggested the
edmontosaurs/anatotitan "mastered" the lambeosaurs by
the late Maastrichtian. I doubt it. Edmontosaurus
already existed in the late Campanian, apparently in
near coastal environments which excluded lambeosaurs.
Farther inland, Hypacrosaurus was still abundant about
3 million years later. Ankylosaurids and nodosaurs
also appear ecologically separated.


 *i.e. besides an impact.
        

_______________________________________________________________
> /o ) \/  Mike Taylor  <mike@indexdata.com> 
> http://www.miketaylor.org.uk
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> 



                
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