Eli5: Animalia phylum. Why are there so many divisions for worms while mammals, fish, amphibians, birds, and reptiles all get lumped into Chordata?

Question

Flatworms (Platyhelminthes), Roundworms (Nematoda), Segmented worms (Annelida), acorn worms (Hemichordata) all get their own phylums. Why?

In: Biology

Answer 1

They were all called “worms” because people were generally ignorant about such animals. It turned out they are very distant groups.

Btw the same applies to “fish”. There’s no animal division that correspond to “fish”. We are more closely related to some fish than these fish are to sharks.