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RE: "Compelling" Paleocene dinosaurs



> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
> Larry Dunn
>
> Does the preservation of the outer bone surface mean
> it's possible that this was a dinosaur that lived,
> what was it, eight million years after the k-t
> boundary?  Is there any way that this is a Cretaceous
> fossil that has shown up in a Paleocene deposit?
>
> And what does this mean about the other fossils that
> have shown up above the k-t bondary?  Does it require
> a re-evaluation?

Where is the "eight million after the K-T" coming from??  The Ojo Alamo was
deposited in the Danian Age (lower Paleocene Epoch).  In other words, this
hadro femur was found stratigraphically in the bottom part of the Stage
immediately above the Cretaceous.  As the text points out, concerning the 8
million year hiatus in the Late K-Early T sequence: "Most of the missing
strata are from the Maastrichtian Stage."

So, in the San Juan Basin, there are late Campanian rocks, then few if any
Maastrichtian rocks, and then picks back up with Paleocene rocks.

Being an isolated durable limb bone, there is indeed the possibility that it
was reworked.  Fassett et al. give a couple lines of evidence (including
lack of wear) as to why they don't think it is reworked, but I would still
find articulated bones and/or footprints which were clearly in Tertiary
rocks much more compelling.

s I think some people were recently saying on the list (gee, who could that
be... :-) good field geology data are extremely important to interpreting
fossils.

As for re-evaluating previous non-avian dino remains in Paleocene rocks: the
observed facts in those cases haven't changed.  They are still isolated
teeth and bones in channel deposits, and could thus be reworked Lancian
material.

Hope this helps.

                Thomas R. Holtz, Jr.
                Vertebrate Paleontologist
Department of Geology           Director, Earth, Life & Time Program
University of Maryland          College Park Scholars
                College Park, MD  20742
http://www.geol.umd.edu/~tholtz/tholtz.htm
http://www.geol.umd.edu/~jmerck/eltsite
Phone:  301-405-4084    Email:  tholtz@geol.umd.edu
Fax (Geol):  301-314-9661       Fax (CPS-ELT): 301-314-7843


>
>
> =====
> Larry
>
> "I've been ionized, but I'm OK now."
>
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