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RE: So many tyrannosaur questions, so little time

> From: Tim Donovan [mailto:msdonovan66@hotmail.com]
> >First of all, where is your data for the "better environment" in North
> >America?  The Nemegt has been interpreted as an Okavango-like delta, and
> >the
> >Okavango is one of THE best spots for large-bodied animals in
> Africa today.
>    But Asia seems generally drier, even in Nemegtian times; Barungoyotin
> beds sometimes "interfinger" with those of the Nemegt.

Of course the Barungoyot does!  That is the model: the deltaic system
representing the Nemegt emptying into the deserts of the Barun Goyot.  That
doesn't make the immediate environment of the Nemegt dry.

> >For that matter, the Campanian E. regalis is bigger than Maastrichtian E.
> >annectens (based on an admittedly small sample size of the former).
> >Therefore we have evidence of at least one case for hadrosaurids
> that does
> >not show the largest species last.
>    IIRC, it has been suggested that E. regalis, which also occurs in the
> Hell Creek, is the adult or larger sex, annectens the smaller.

The Lancian reports of "E. regalis" are apparently mistaken.  As for sexual
dimorphism as an explanation: we'll have to wait and see.

> > >   Unfortunately it lacks datable materials, even if the other
> svitas and
> > > gorizonts have them. Biostratigraphy must play a big role.
> >
> >Biostratigraphy, yes.  Dinosaur biostratigraphy, NO!  To do such gets you
> >(again) into a circularity argument.
> >
> >Furthermore, what makes  you think that the units *lack* datable
> materials?
>    I meant only the Nemegt.

Which also may indeed have datable material.  Just because the dating work
HASN'T been done doesn't mean that it CAN'T be.

                Thomas R. Holtz, Jr.
                Vertebrate Paleontologist
Department of Geology           Director, Earth, Life & Time Program
University of Maryland          College Park Scholars
                College Park, MD  20742
Phone:  301-405-4084    Email:  tholtz@geol.umd.edu
Fax (Geol):  301-314-9661       Fax (CPS-ELT): 301-405-0796