lampreyectothermic fish with a partial backbone; does not have jaws; skeleton is made of cartilage.

Do lampreys have vertebrae?

Therefore, it was suggested that the name 'Vertebrata' should only refer to the clade including lampreys and gnathostomes, which both possess vertebral elements and whose sister group are hagfishes, all three taxa being included in the Craniata [7].

Do lampreys have an endoskeleton?

Hagfish and lampreys are unusual for modern vertebrates in that they have no jaws and their skeletons are neither calcified nor strengthened by collagen — the cartilaginous elements of their endoskeleton are composed of huge, clumped chondrocytes (cartilage cells).