Are lancelets vertebrates

Lanceletes are invertebrates, because they do not have any spine consisting of a chain of vertebra (vertebral column).

They are however related to vartebrates being a mamber of the fylum (major animal group) chordates (chordata) of which also vertebrates (vertebrata) are a member.

Instead of a vertebral column they have a rod at the same place made of robust connective tissue, a notochord. The spinal cord (nerve string) of this animal is not encased in this primitive spine, but lies posterior to it.

This notochord later developed to a spine consisting of a chain of vertebra in the higher species. The early stages of the embryo of all vertebrates still have a notochord which during the fetal development gives rise to a real spinal column.