Flatworms (Platyhelminthes), Roundworms (Nematoda), Segmented worms (Annelida), acorn worms (Hemichordata) all get their own phylums. Why?
In: Biology
it’s in the name: Chordata, basically everything in there has a “spine” or more accurately a notochord among other shared features, and the body plans are all built around it. The lowest common denominator if you will. “worms” on the other hand are such a simple body plan (essentially a tube) that many things can be “worms” without sharing a “lowest common denominator” more specific than being “Animalia”
imagine if you had a large bag full of marbles and other various polished rocks, the marbles are in a huge variety of designs from super simple to very very intricate. Technically everything in the bag is some kind of “rock”, and they are all at least somewhat round and smooth. The next best categorization would probably be what each is made of. This groups all marbles, simple, complex, large, or small into “glass” and all the other polished rocks are grouped into “sandstone” or “granite”, etc… You could make the argument to group them into “glass” and “not glass” but the same could be said for “granite” and “not granite”, it would be pointless. Though on the surface (outside of your classification) you could call out that all of the glass ones are “marbles” and everything else are “stones” much like how so many things fit into “Chordata” but there are many “everything else” with a simpler “worm like” body plant that fit into other categories
Edit: reddit seemed to die right around when I was trying to post this, please ignore if it posts duplicates because reddit is a very well built website that wouldn’t possibly do such a thing lol
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