Conodonts are an extinct group of jawless vertebrates whose tooth-like elements are the earliest instance of a mineralized skeleton in the vertebrate lineage, inspiring the 'inside-out' hypothesis that teeth evolved independently of the vertebrate dermal skeleton and before the origin of jaws.

Do conodonts have bone?

The spine of the conodont contained no bone, but it was a stiff structure made of turgid protein cells called a notochord.

What vertebrates do not have a jaw?

Cyclostomes: Hagfish and Lampreys

Members of both groups have cartilaginous skulls, qualifying them as true crown-group vertebrates, but lack jaws. In fact, they are the only two groups of extant vertebrates that lack jaws.