Re: Fastovsky vs Archibald

[Tim Donovan <uwrk2@yahoo.com>]

--- GUY LEAHY <xrciseguy@prodigy.net> wrote:

> It's also important to note we don't know yet if
> Campanian dinosaur faunas in other parts of North
> America (or anywhere else, for that matter) were
> also more diverse than their Maastrichtian
> counterparts.  In New Mexico/Utah, for example, the
> only known hadrosaurs from Campanian units are
> Kritosaurus and Parasaurolophus,


  Didn't Witzke mention a giant lambeosaur from the
Campanian of the same region?


> a far smaller # of
> genera than has been collected from Judith River/Two
> Medicine sediments of the same age.  None of the
> Hell Creek equivalents in this region have yielded
> hadrosaur remains which have been to date identified
> to genus.  


  A large hadrosaur humerus from the Naashoibito is
considered hadrosaurine, which suggests remaining
hadrosaurs were the same as in the Hell Creek and
elsewhere.


> > 
> > stratigraphically refined study addressing this
> question has 
> > concluded 
> > that dinosaur diversity was unchanged up to the
> K/T boundary"
> > 
> > and Archibald: "In the last 10 million years of
> the Cretaceous, 
> > but 
> > well before the K/T boundary events, the most
> recent compilations 
> > show an 
> > unequivocal decline in the diversity of dinosaur
> species."
> > 
> > Hard to see how both of these statements can
> co-exist. 
> 
> 
> Au contraire.
> Based on current data, both Archibald and Fastovsky
> are correct. But
> they are essentially talking past each other.
> 
> Archibald is correct in noting that taxa counts show
> a decrease in
> dinosaur diversity within the last 10 million years
> of the Cretaceous
> (this is particularly apparent when comparing the
> dino fauna of the
> Judith River/Two Medicine Formations with the dino
> fauna of the later
> Hell Creek Formation). Ergo, Archibald is looking at
> extremely long-term
> trends.
> 
> Fastovsky is correct in concluding that dinosaur
> diversity WITHIN the
> Hell Creek Formation was not in decline up to the
> K-T boundary. In other
> words, even though their were fewer dino taxa in the
> Hell Creek Formation
> compared to earlier times, there is no evidence that
> this group was in
> steady decline up to the terminal layer. Therefore,
> Fastovsky is looking
> at a much shorter trend (~2 million years at most),
> and noting that not
> much changed.
> 
> That said, some workers have claimed that a Hell
> Creek nodosaur went
> extinct before the K-T boundary. But considering
> that ankylosaurids are
> generally uncommon in the Hell Creek Formation,
> there is a good
> possibility that the proposed premature nodo
> extinction may in fact be
> only an artefact of sampling/collecting.
> 
> 
> 
> --
> 
> 
> 
> 


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