Agnathan and Lamprey

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

Lamprey and agnathan are semantically related. In some cases you can replace term "Lamprey" with "Agnathan", this nouns are similar.

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

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