Re: Fastovsky vs Archibald

[Tim Donovan <uwrk2@yahoo.com>]

--- Phil Bigelow <bigelowp@juno.com> wrote


> The Scollard Fm. may have been deposited far from
> the WIS. Some workers
> even claim that the Scollard, itself, had closed off
> the Seaway. 

But what about the Frenchman, farther east? I don't
think there is any doubt that the Scollard was farther
inland than the Hell Creek, and represented a cooler,
drier environment.


> the climate would have
> been harsher than it
> was further to the south.
>
> The Hell Creek Formation was deposited adjacent to
> the WIS, which
> moderated its climate.


 Right. Regarding flora, IIRC Wodehouseia is common to
both units. But I only wanted to make the point that
the Scollard has virtually the same dinosaur taxa as
the Hell Creek, despite environmental differences
formerly associated with much different hadrosaur
types. Edmontosaurus was the predominant hadrosaur in
near marine environments since the Campanian.  Other
taxa lived farther inland. The absence of such taxa in
the inland Scollard suggests they were gone by the
latest Maastrichtian, causing Edmontosaurus to occupy
their habitats.
 
 
>   Migration away
> from the Hell Creek region or increased geographical
> restriction within
> the Hell Creek region are two equally parsimonious
> interpretations of
> that same data, and in theory they are both provable
> hypotheses.  


 Or falsifiable. As I wrote before, Russell suggested
that the apparent absence of nodosaurs in upper
Lancian sediments was due to regression, causing the
near coastal nodosaurs to abandon the Hell Creek etc,
and migrate farther eastward with the "receding" sea.
But how likely does that explanation now appear in
light of evidence for transgression late in Lancian
time?


>But it
> is nearly impossible to identify an undisputed
> extinction horizon within
> a formation.  


  Interestingly, Edmontonia disappears in the 
Ferris at the level where a change in sedimentology
precludes further reworking. It may have been gone
long before then.
 
> All that we can say for certain is that, so far, no
> articulated nodosaur
> or lambeosaur skeletons have been collected from the
> upper part of the
> Hell Creek Formation. 

 Or equivalents, AFAIK.


> We don't even have enough
> samples to correlate the
> known nodosaur occurrences with depositional
> environments.  


 Russell noted long ago that nodosaurs are often found
in marine sediments. Ankylosaurids were often well
inland. They were numerous in Mongolia, where
nodosaurs are unknown.



                
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