Nature of the fossil record

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I really don't want to belabor this point (and I certainly don't want Doug
to feel like he's being picked on) but Doug's comment shows just how
insidious the S&L Effect is and how easy it is to see whatever we want to
see in it's image.  Is the Signor-Lipps Effect PRIMARILY a preservation
phenomenon?  Any particular Signor-Lipps pattern might be due to
differential preservation.  But then again it might be due to sample
size/relative abundance interactions, or ecological changes.  That's the
problem with negative evidence.  You simply can't know precisely why
something is not there.  Signor and Lipps (1982) list three sources for the
effect without indicating which one is dominant.  Within it's domain the
S&L Effect is simply a statement of uncertainty.  But there must be a
domain outside of which the S&L Effect can be ignored.  If this isn't true
then I guess I don't understand how biostratigraphy is possible.

Norm MacLeod



>to reinterate what Jere has said in a slightly different way - the point
>of the Lipps(-Signor) Effect is that is establishes the correct null
>hypothesis against which to measure the observed patterns in the fossil
>record.  Contrary to Peter Harries comments, the L(-S) Effect is PRIMARILY
>a preservational phenomenon.  The effect is exacerbated by collecting
>bias and can be reduced by increased collecting effort.  However it cannot
>be completely negated by increased collecting.  Correctly identifying the
>null hypothesis is critical in all of this, and is all to infrequent in
>paleontology.
>Doug Erwin



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Norman MacLeod
Senior Research Fellow
N.MacLeod@nhm.ac.uk (Internet)
N.MacLeod@uk.ac.nhm (Janet)

Address: Dept. of Palaeontology, The Natural History Museum,
                     Cromwell Road, London, SW7 5BD

Office Phone: 071-938-9006
Dept. FAX:  071-938-9277
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