[Taxacom] How do fossil mollusc taxonomists manage?
barry_roth at yahoo.com
Thu Sep 24 00:23:53 CDT 2009
... by the seat of our pants, perhaps. In spite of rampant convergence and parallelism in shell form, I find that a close reading of fossil and Recent shell morphology often generates compelling evidence for identification and taxonomic assignment. There is often enough independent evidence (the thermal and precipitational ranges of Recent members of the genera represented in a fossil faunule; the climatic facies of associated plant or animal remains; etc.) to make us feel we're on the right track.
I have been encouraged by molecularly based phylogenies to look at, for example, family assignments for fossils that might not have occurred to me before.
Not sure this addresses any of the theoretical issues, but it represents the practice as she is done.
--- On Wed, 9/23/09, Stephen Thorpe <s.thorpe at auckland.ac.nz> wrote:
OK, if the argument is this (see below), then it is stronger:
Molecular evidence applied to extant hominids shows that the morphological characters that we have to rely on (for lack of any alternatives) in the case of fossil hominids are completely unreliable indicators of relationships. But does it really show that?
Presumably, the case would be similar for molluscs, because conchological characters alone are not good for extant molluscs, but it is all we have in the case of fossils. So, how do fossil mollusc taxonomists manage?
Presumably, if you accept that molecular evidence is a priori definitive of relationships (BIG assumption), then you need to try to find morphological characters that are congruent with the molecular results (in the case of extant taxa, and then apply the morphological results to fossils). If none can be found, then there is presumably little or no point in trying to classify fossils phylogenetically ...
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