ABSTRACT
In order to make a proposed phylogenetic hypothesis as robust as possible it is advisable to do global outgroup comparisons, instead of using only the local outgroup method. The phylogenetic analysis reveals that the strength of a presumed apomorphic character is in many cases weakened by the fact that some species only distantly related to the proposed monophylum also show the apomorphic character state. The species of marine triclads presented in the foregoing taxonomic sections represent all members of the monophyletic infraorder Maricola known to date. The monophyly of the Cercyridae is at present only supported by one underlying synapomorphy, although its evolutionary reality is strongly suggested by the genealogical relationships within the group and also by a few character state distributions of possible underlying synapomorphies. The phylogenetic hypothesis proposed recognizes within the Maricola three major monophyletic groups which stand in a particular genealogical relationship to each other, viz. Cercyroidea, Bdellouroidea, and the Procerodoidea.
