Re: Fastovsky vs Archibald

[Phil Bigelow <bigelowp@juno.com>]

On Mon, 20 Jun 2005 09:16:09 -0700 (PDT) Tim Donovan <uwrk2@yahoo.com>
writes:

> The discovery of
> "Aublysodon" remains at the K-T suggests T. rex
> survived to the end too, wouldn't you say? :)


Well, it depends.

1) Are the remains single elements or are they articulated? (single
elements may suggest older reworked material).

2) What is the depositional environment where the remains were found (if
the fossil is a single element, then channel sandstone or point bar
deposits suggest older reworked material).

3) Is the iridium layer ACTUALLY near the site of the remains (in other
words, was the presumed boundary layer actually tested for iridium?; if
it contains iridium, can the layer be easily traced to a point directly
above the remains?).  Dirty little secret:  a lot of so-called "boundary
beds" in the Hell Creek Fm., are actually INTERPRETED to be there.  The
iridium layer is in reality a discontinuous layer (due to paleoerosion),
and workers sometimes do extrapolation.  It's not a sin to extrapolate
time boundaries over extremely short distances, but it should be noted in
the paper if it was done.  However, extrapolating time boundaries over
longer distances is *not* a good thing.

4) How far below the confirmed Ir-containing boundary layer are the
remains?  In the Hell Creek Fm., a one-meter stratigraphic separation may
represent a time span of only one year OR it may represent a time span of
10,000 years.  It all depends on #2 (above).  So, does making it to
within one meter of the K-T boundary mean that the taxon was present when
the big rock fell?  Not necessarily.

5) Is the material properly taxonomically identified?  In the case of
_"Aublysodon"_, that is problematic.  It would be more scientifically
accurate to publish the occurrence as Tyrannosauridae indet., rather than
as a genus (that is currently in dispute).


> But what
> about Edmontonia?


The same rules apply.

<pb>
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