A rare, half-billion-year-old fossil gives us a clue to how a bizarre marine invertebrate can possibly be related to humans. In a study published on July 6 in the journal Nature Communications, Harvard University researchers identified a prehistoric specimen in a collection at the Natural History Museum of Utah as a tunicate, or sea squirt. The preserved invertebrate, which was originally discovered in the rugged, desert-like landscape of the House Range in western Utah, can be used to understand evolution mysteries that go way back to the Cambrian explosion.

“There are essentially no tunicate fossils in the entire fossil record. They’ve got a 520- to 540-million year-long gap,” says Karma Nanglu, an invertebrate paleontologist at Harvard. “This fossil isthe first soft-tissue tunicate in, we would argue, the entire fossil record.”

https://www.popsci.com/environment/tunicate-fossil-cambrian-explosion/#:~:text=A%20500%2Dmillion%2Dyear%2D,the%20history%20of%20animal%20life.