The answer
is arthropods have had more time to co-evolve with land plants than have
vertebrates. Analysis of genes shows that their sequences are quite similar,
and these sequences differ from those of the lophotrochozoans and
deuterostomes. Between the annelids and
arthropods will probably be viewed, in retrospect, as an instance of an
evolutionary relationship that modern scientists had ʺset in stone, ʺ now
having crumbled.
