The foldworms, or Plicohelminthes, typically fill up niches on Gossipiboma that are occupied on Earth by the Platyhelminthes, or flatworms, being parasites, small marine carnivores, and even interstitial fauna. The name "foldworm" comes from the unusual structure of the mouth, which, during the animal's development, folds over the blastopore, which becomes the mouth later on. The internal anatomy of the generalized foldworm is much like that of a tri- or polyclad flatworm, with two lateral nerve cords, and branching gut diverticula, but the urogenital systems are very distant.

A. Thick cirrate folder--A very tiny, almost gutless form of interstitial foldworm. The reason for the coloration is unknown.
B. Planetarian
C. Snake fluke--A large parasitic foldworm that has inverted itself so that its mouth is ventral and a spiny sucker is dorsal, allowing it to effectively absorb nutrients from the notopeltid heart while remaining in place.
D. Valgaprott
E. Torpaglav