Re: On the subject of mysterious absences...The Answer

[David Marjanovic <david.marjanovic@gmx.at>]

I feel like a smart teacher in a classroom full of smart kids... :o)

> The error is a logical one as well as a failure of imagination. [...]
> I can't see any reason why xenacanths would be restricted to a narrow
> salinity range, especially if their habitat included seasonally
> flooded forest land like the Amazon basin. Would be an adaptive
> advantage to be flexible.

So you're saying the second conclusion does not follow from premises 3 and 4:

> > Premise 3: Anthracosaurs lived in freshwater.
> > Premise 4: Xenacanthids always occur together with anthracosaurs or 
> > other amphibians (premise 2).
> > Conclusion: Therefore xenacanthids lived in freshwater.

You are right, but that's not what I meant, and the conclusion still follows if 
you regard it as a probability statement instead of as the absolute that I 
wrongly implied: "therefore, when we find reasonable numbers of well-preserved 
xenacanthid remains, we are probably dealing with a freshwater deposit, unless 
of course we find additional evidence that contradicts this conclusion".

There's a much bigger error in the chain.
-- 
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