Chordate Classification

[spikezz]

Supposedly the only two subphyla of nonvertebrate chordates are Urochordatea (tunicates) and Cephalochordata (lancelets); however, jawless fishes of the order Cyclostomata (e.g. lempreys and hag fishes) also do not have vertabrae and keep their notochords. Why is this so? Cyclostomata are considered one of three groups of fishes.

[mith]

I don't see a question

[pedro21101]

Hello
I think cyclostomata own rudimental chondroid vertebrea or their basics which are located around the chorda. Also the other name for phylum vertebreta is usually craniata. That could diferentiate cyclostomata from the cephalochordata which i suppose have no cranium. (though i dont know if cyclostomata own cranium, i think they do because of that term craniata)
This is only suggestions (i hope not so confusing)