How are nematodes and platyhelminthes similar?

Some of the few similarities between the two groups:

• Both are true animals and have all the features that come with that (Eumetazoa)
• Both have bilateral symmetry–are roughly the same left to right–and are a member of clade Bilateria
• Both are extremely enthusiastic as parasites
• Neither have any hard parts and have little fossil record
• Both are roughly worm shaped, although the occasional platyhelminth gets creative with this
• Both are triploblastic–they have three cell layers during development, unlike cnidarians like anemones, which are diploblastic.