Meet your earliest known ancestor: Saccorhytus
How is Saccorhytus related to humans? Humans are vertebrates and so are one of the major groups that collectively define the deuterostomes, a group that also includes animals that are quite different from humans, such as sea-urchins and sea-squirts, all ultimately descended from an original deuterostome. Our argument is that Saccorhytus is close to this ancestral form, and so is the most primitive known deuterostome.
via https://www.researchgate.net/blog/post/meet-your-earliest-known-ancestor-saccorhytus