It's difficult to pinpoint the *very first* organism with a vertebra, as the fossil record is incomplete. However, we can look at some early examples:

* Conodonts: These tiny, eel-like creatures lived around 500 million years ago. They are thought to be among the first vertebrates, but their skeletons were made of a mineral called apatite, which doesn't fossilize well. We mostly know them from their teeth, which are well-preserved.

* Haikouichthys: This fish-like creature lived about 525 million years ago. It had a distinct head, a notochord (a flexible rod that predates the vertebral column), and possible gill slits. It's considered a strong contender for an early vertebrate.

* Myllokunmingia: This is another fish-like creature from the same period as Haikouichthys. It also had a notochord, but its skull and vertebral column are more rudimentary than those of Haikouichthys.

The exact evolutionary path leading to vertebrates is still debated by scientists. These early creatures, along with other fossils from this period, provide clues about the transition from invertebrate to vertebrate life.