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Re: Albertosaurinae survival
On Thu, Jun 26, 2008 at 2:02 PM, John Schneiderman
> Try these web links for information:
Wow, that's a lot of sites. Thanks - this is a really rich response.
I'll pore over all of them as I get the chance.
> I'm a firm believer that the Manson Impact event effectively cleared the
> slat so to speak of North America's European style dinosaurs [dryptosaurs,
> iquanodontids, nodosaurids, hadrosaurs] only to have them replaced by Asian
> immigrates [ tyrannosaurs, ornithomimids, ankylosaurs, ceratopsians,
> lambeosaurines, therizinosaurs, dromeosaurs].
Well, hold on . . . the impact was at 74 mya, right? So mid-late
Campanian. If we're talking about Laramidia specifically (since we
know *Dryptosaurus* was around in the latest Maastrichtian of
Appalachia), then nodosaurs and hadrosaurines are known from both
before after that event, and with no nodosaurs known from the later
Late Cretaceous in Asia, I'm not sure we can claim that N. American
nodosaurs from that timeframe have immediate Asian predecessors.
Possible, certainly, an interesting possibility, definitely, but not
too solid yet (AFAIK) . . .
Basal therizinosaurs are also known from the Barremian (*Falcarius*)
and Turonian (*Nothronychus*) of N. America, so a re-immigration
scenario isn't *necessary* to explain their later presence on that
continent - although it could still be feasible if the impact was
truly that severe (or if they were extirpated earlier for some
reason). The same thing applies to ankylosaurids, with a very basal
member (*Cedarpelta*) being known from Early Cretaceous N. America,
and to dromaeosaurs, with both velociraptorines (*Deinonychus*) and
dromaeosaurines (*Utahraptor*) known from the Early Cretaceous. And,
finally, what about the ceratopsid teeth from the Aptian Arundel Clay,
and what about the Turonian *Zuniceratops*? Clearly ceratopsians, even
rather derived near-ceratopsids, were present in N. America well prior
to the Manson event.
It's possible that all these groups got wiped out and then
re-immigrated, but I don't know that current evidence would lend much
support to the idea.
> Hope this helps.
> John Schneiderman
Heh, with all those sites you provided, I can't imagine *not* finding
something useful. Thanks again for all the info.