Re: Fastovsky vs Archibald

[Tim Donovan <uwrk2@yahoo.com>]

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

 
> I agree.  And the Scollard Fm. should be presumed to
> be a separate and
> unique paleoecosystem at least until proven
> otherwise by empirical
> evidence.

 It did apparently represent a somewhat different
paleoenvironment but it had an essentially typical
Lancian dinosaur fauna, and flora.

 
> Isn't _Edmontosaurus_ also found in the Saint Mary
> River Formation, an
> upper floodplain unit which abuts the Laramide
>uplift?

 AFAIK the taxa all appear to be lowland types,
including Edmontonia. That was in the early
Maastrichtian, so the coast wasn't so far to the east.

>Find a
> North Dakota or South
> Dakota section that is in the upper part of the Hell
> Creek Fm. 

 No nodosaur has ever been found in upper Hell Creek
or equivalent strata anywhere, despite environmental
conditions which were probably more favorable than at
the start.


 
> "Gone" in a sense, perhaps.  "Extinct", not so sure.

 How else can you explain their apparent absence
toward the end?


 > 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. 

  While rereading the recent report of a Lancian
lambeosaur, I noticed it was found in a coastal
environment in Park County, WY. That certainly
suggests the specimen predates the "classic" Lancian
deposition farther east, maybe by 2 million years or
so, and thus has has no relevance to this issue.





> Which may be reflective of their paleogeographic
> range, or it may be
> reflective of taphonomic concentration.  I favor the
> latter hypothesis. 
> Nodosaurs (and ankylosaurs) are often found laying
> on their backs both in
> fluvial units and marine units. 
 

  They certainly aren't found in Mongolia, where
ankylosaurids are numerous. A nodosaur is, I believe,
now known from Kundur, so it appears that nodosaurs,
like many other dinosaur taxa, were able to traverse
the Bering area. But they apparently couldn't exist in
the far inland habitats of central Asia. Or in the
Scollard.



> Their thick
> armored hide may have precluded the carcass from
> bursting. 

 What about the unarmored belly?

 


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