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Re: Fastovsky vs Archibald
--- GUY LEAHY <email@example.com> wrote:
> Since lambeosaurines (?Hypacrosaurus/?Lambeosaurus
> laticaudus) are known from marine sediments
> (including a possible lambeosaurine from the upper
> Maastrichtian New Egypt Formation of New Jersey) I
> suspect lambeosaurine environmental preferences were
> fairly broad... ;-)
Could be. Remember Wegweiser's report of a
lambeosaurine from a coastal Lancian site? But if near
marine habitats were preferred by late Maastrichtian
lambeosaurs, why aren't they more abundantly preserved
in the western interior? I don't know the level at
which this lambeosaur occurs in the Lance. Even if it
is stratigraphically high, I think one can still make
a case for gradual extinction in that lambeosaurs
appear greatly diminished in numbers and ecological
importance by the late Maastrichtian.
> As I'd noted in an earlier
> post, we really do not have a good idea of what
> Campanian/Maastrichtian dinosaur diversity trends
> were anywhere outside of Alberta/Montana/South
> Dakota in North America.
I think hadrosaur diversity waned in Asia as well as
in North America. Lambeosaurs seem relatively abundant
in the Djadokhta equivalent beds at Laiyang but
certainly not in the younger Nemegt.
> In any event, if Hypacrosaurus and Edmontosaurus did
> not prefer the same habitats, the presence of
> Edmontosaurus in the Scollard Formation might
> suggest that the Scollard paleoenvironment was not
> to the liking of Hypacrosaurus.
I think it's noteworthy that it appears absent or
very rare in all environments post unit 4. Some may
suggest that lambeosaurs were still thriving in the
intermontane environments where diagnostic hadrosaur
material is unknown. But I note that lambeosaurs were
virtually absent in the Nemegt at a time when
Saurolophus was able to migrate. And Barsboldia might
> Wouldn't surprise me... other hadrosaurs may have
> had short temporal ranges. In addition, to the best
> of my knowledge, all specimens of Tyrannosaurus rex
> appear to be from the upper unit.
Are you sure? I thought a juvenile T. rex is known
from the bottom of the Hell Creek.
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