Agnathan and Lamprey eel

Agnathan noun - Eel-shaped vertebrate without jaws or paired appendages including the cyclostomes and some extinct forms.

Lamprey eel and agnathan are semantically related. In some cases you can replace phrase "Lamprey eel" with "Agnathan", this terms are similar.

Lamprey eel noun - Primitive eellike freshwater or anadromous cyclostome having round sucking mouth with a rasping tongue.

Agnathan and lamprey eel are semantically related. You can use "Agnathan" instead a noun phrase "Lamprey eel".