Agnathans in the class Petromyzontida are members of one of our early lineages in vertebral evolution. How does this clade fit into the vertebral evolutionary tree?

Agnathans in the class Petromyzontida are members of one of our early lineages in vertebral evolution. How does this clade fit into the vertebral evolutionary tree? This group has an interesting life cycle. Provide a detailed description of the general life cycle for this taxon, and make it clear what it means when we say they are anadromous.

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