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

The definition of “worm” is basically “elongated bilateral invertebrate with no legs”. This category is so loose, that many animals that are not closely related will fall into it.