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Re: The timing of stegosaur extinction



--- Michael Mortimer <mickey_mortimer111@msn.com>
wrote:

> Tim Donovan wrote-
> >
> >  Gurvan Eran, Tevsh, Undurukhin and Tsagantsab
> >formations of Mongolia. I don't know in which of
> those
> >units or what other fossils show equivalence,
> though
> >Tugulu turtles "seem little changed from the late
> >Jurassic."
> 
> The only dsungaripterid Unwin and Bakhurina (2000)
> report from anywhere in 
> Mongolia is "Phobetor" parvus, which was previously
> named Dsungaripterus 
> parvus.  This does not mean it can be used to
> correlate stratigraphy with 
> Dsungaripterus weii though.
> Your turtle statement is too vague to be useful.


 AFAIK there are no stegosaurs in the c Barremian age
Mazongshan beds, nor in Mongolian or Chinese beds of
late early Cretaceous age, such as those which yielded
Chilantaisaurus. Is there any evidence that the
Lianmuqin is younger than Valanginian?


> 
> > > >K-Ar dating etc indicates a
> > > >Berriasian-Valanginian age for the Mongolian
> beds.
> > >
> > > Berriasian-Aptian, according to dates in
> Shuvalov
> > > (2000) for the Tsagantsav
> > > Svita.  Not very precise...
> >
> >
> >  See pages 259 and 271. He made it clear that the
> >Tsagantsav svita is dated at Berriasian-Valanginian
> on
> >the basis of K-Ar dating and fossils. Also that
> >Tsagantsabian deposition began before the end of
> the
> >late Jurassic.
> 
> Ah, but his table 14.2 includes absolute dates which
> are as recent as Aptian 
> (e.g. upper part of Tsagantsav Svita 120 +/- 5 Ma). 
> The Aptian started 125 
> Ma (Gradstein and Ogg, 2004).


  That doesn't make much sense, since the youngest
putative Tsagantsabian dates overlap with those given
for the younger Huhteeg Gorizont.  Shuvalov was aware
of those younger dates but evidently didn't take them 
seriously. IGEM dates have big margins of error and
some are probably inaccurate. I note Lucas just used
130 Ma, apparently based on an average value.


> 
> > > >  IIRC K. Carpenter mentioned a new, Aptian age
> for
> > > the
> > > >Yellow Cat onlist.
> > >
> > > Where?  A search for "Carpenter" "Aptian" Yellow
> > > Cat" came up with no
> > > relevent posts.
> >
> >   I just relocated it myself and will forward it
> to
> >you. I see the Yellow Cat could be either Barremian
> or
> >Aptian. If it is Barremian the NA stegosaurs
> >apparently disappeared before then.
> 
> I await this forwarded post.

 Actually it wasn't put onlist but you should have it
by now.



> 
> Mickey Mortimer
> 
> 
> 



        
                
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