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Re: PDF-request: Original description of Lagosuchus and/or Marasuchus

On Apr 10, 2010, at 5:56 AM, David Peters wrote:

To your point, if simply coding from the literature won't work this time it means the literature is not only wrong, it's >so< wrong that topology tumbles. And now is a good time to remind ourselves that the literature was written from >first hand observation<.

So, what is your logic leaving us with? If first hand observation won't work (see above), plane tickets would be a waste of money. Right? Yes, it's a vicious unwinnable Catch-22 you are creating here.

Not quite. Bill Parker was indicating that coding from the literature is, itself, the step of insufficiency. The literature was written from first hand observation, but writing based on that literature is no longer first hand observation. The best way to re-evaluate former first hand observation is to make new first hand observations of our own - that is, go see the specimens for ourselves.

The literature is important, of course, and it is completely sensible to rely on it for many types of information. However, when coding a phylogenetic reconstruction, using the literature can be tricky business. Some methods do this exclusively of course (supertrees and supermatrices, for example) but these methods often have goals other than supplying a novel, robust topology (supertrees, for example, are mostly a method for quantifying the historical record of published phylogenies up to that time, often as a way of evaluating consensus in the literature. This is a different goal than trying to actually reconstruct ancestry).

It is also worth pointing out that some methods of coding from the literature are more robust than others. For example, if one is simply adopting the data matrix supplied by another author, and combining it with others (supermatrix), then you are only assuming that the prior authors were accurate. This has its own set of problems, but can be workable in some cases. However, trying to create new codings from the literature (say, for example, by trying to code from a photograph or other second-hand source) is exceptionally difficult to do accurately, and there will almost always be features that are not accurately represented in a 2D photo or other such representation. I believe this is what Parker was suggesting should be the impetus to travel and observe specimens directly.



Michael Habib
Assistant Professor of Biology
Chatham University
Woodland Road, Pittsburgh PA  15232
Buhl Hall, Room 226A
(443) 280-0181