The first species, Xenoturbella bocki, was described around 1949 off the coast of Sweden, and lumped in with the flatworms. In the 1990s, people decided that it could be a mollusk, based on DNA ...

Read more: Frozen prehistoric mummy stuns scientists by remaining perfectly preserved for 5,300 years The animal's shifting evolution began when the first species, named Xenoturbella bocki ...