A: Morphological Phylogeny

question 16

Multiple Choice

A: Morphological phylogeny.
B: Molecular phylogeny.
In the traditional phylogeny (A) , the phylum Platyhelminthes is depicted as a sister taxon to the rest of the protostome phyla and as having diverged earlier from the lineage that led to the rest of the protostomes. In the molecular phylogeny (B) , Platyhelminthes is depicted as a Lophotrochozoan phylum. What probably led to this change?

• A) Platyhelminthes ceased to be recognised as true protostomes.
• B) The removal of the acoel flatworms (Acoela) from the Platyhelminthes allowed the remaining flatworms to be a monophyletic clade clearly tied to the Lophotrochozoa.
• C) All Platyhelminthes must have a well-developed lophophore as their feeding apparatus.
• D) Platyhelminthes' close genetic ties to the arthropods became clear as their Hox gene sequences were studied.

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