Worms as a group are more genetically diverse than mammals, birds, fish, and reptiles combined.
Those 4 groups are part of one phylum the Chordata, whereas "worms" are comprised of 4 separate phyla.
1. Platyhelminthes (flatworms)
2. Nematoda (roundworms)
3. Annelida (earthworms, polycheates)
4. Nemertea (ribbonworms)
Basically, you're more closely related to fish than some worms are to one another. Huge diversity in this group.