[Taxacom] more science nonsense

[David Campbell]

The fossil indicates that the clade was present in the southern hemisphere
at the time.  Lacking a corresponding northern hemisphere find, it very
weakly supports a southern origin.  But this depends a lot on the dispersal
abilities, the level of knowledge about the group, and other factors.
Large seabirds can easily travel almost anywhere, so finding one in a
particular place is not particularly informative, and the avian fossil
record is rather patchy.  Thus, it is extremely weak evidence.  In
contrast, extensive records of a shallow marine invertebrate clade with
hard shells and high abundance in one region but not another would be much
better evidence of a region of origin.  Most taxa will originate in a
particular region, simply because that's where a particular mutation first
occurred (although gradual replacement with interbreeding with other groups
is possible, making the identification of a specific point in time or space
of origin difficult.)


> --
Dr. David Campbell
Associate Professor, Geology
Department of Natural Sciences
Box 7270
Gardner-Webb University
Boiling Springs NC 28017