Hemichordates also share many of the same characteristics as chordates - a group of animals that includes humans - with the name hemichordate roughly translating to 'half a chordate.
Acorn worms are themselves part of the hemichordates, a group of marine animals closely related to today's sea stars and sea urchins.
In preliminary studies, Shu Degan of Xian Northwest University places Yunnanozoon in another phylum, the hemichordates
, which includes the modern acorn worms.
Professor Max Telford, from the UCL Department of Genetics, Evolution and Environment, and joint leader of the research said: "Because the simple Xenacoelomorpha are descended from the same ancestor that gave rise to complex groups such as vertebrates, echinoderms and hemichordates
, these simple worms must have lost a lot of the complexity that they originally possessed.