Apomorphies and Synapomorphies between Snails, Earthworms and Ants

One would assume that garden snails, earthworms and ants are three very different animals based purely on external morphology. However, closer analysis of features common to all three indicate that they are indeed much more closely related than apparent from appearances. This is confirmed by the evolutionary classification of animals, which shows that the three all belong to a certain phylum, with the differences being the result of evolutionary development of apomorphies, or derived states. Consideration of the synapomorphies between the three highlight this, and thus show that they are different from such things as sea stars and sea squirts, which belong to different phyla.

Garden snails, which belong to the phylum ‘Mollusca’ and the class ‘Gastropoda’, earthworms (Annelid, Oligochaeta) and ants (Arthropoda) (Anon. 2003) all belong to the ‘Coelomate’ phylum (Strickberger, 1990). Coelomates are characterised by the presence of a mesoderm, layer between the ectoderm and...