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Re: Everything you know about the Iren Dabasu age is (right)
I couldn't agree more... give me ammonites and pollen
over dinosaurs any day (strictly for biostratigraphic
purposes, of course)... :-)
Magnetostratigraphy and radiometric dates are even
better, since one does not have to worry about time
transgressive first/last appearances producing errors
in age estimations.
--- Michael Mortimer <firstname.lastname@example.org>
> Tim Donovan wrote-
> > Iren Dabasu has other taxa in common with the
> >Bayanshirenian beds of Outer Mongolia. Erlikosaurus
> >and Segnosaurus are known from Baishin Tsav as well
> >Iren Dabasu. Segnosaurus is also known from Khar
> >Hotol, where the boundary between the Bayanshiree
> >Djadokhta formations occurs.
> There has been no published evidence for any
> Erlikosaurus or Segnosaurus
> remains outside of their holotypes and (in
> Segnosaurus) paratypes. Sure
> Currie and Eberth reported elements which were
> 'identical' in 1993, but then
> in 2001 and 2002 we get two new Iren Debasu
> therizinosauroids. Until the
> old remains are compared with these new taxa, the
> referral is very weak.
> Remember, Mononykus, Avimimus, Saurornithoides and
> Velociraptor have all
> been reported from Iren debasu as well, and are all
> Djadockhta/Nemegt age.
> But Currie and Dong (2001) later modified Currie and
> Eberth's referral from
> Saurornithoides to Troodontidae indet.. I've seen
> figures of the Iren
> Debasu Avimimus remains, and how are we to tell if
> they're Avimimus
> portentosus, A. sp. nov., or another genus of
> avimimid? They differ a bit
> from the A. portentosus specimens, but determining
> what it means is pretty
> Basically, the take-home message is that dinosaur
> biostratigraphy sucks and
> should not be used except very generally.
> Invertebrates, pollen,
> charophytes - those are useful.
> Mickey Mortimer