Yunnanozoon

Yunnanozoon lividum (Yunnan + Greek ζῷον "zôion", "lividum"; "livid animal of Yunnan") is an extinct species from the Lower Cambrian, Chengjiang biota of Yunnan province, China. It is thought of as a deuterostome suspected of being either a hemichordate or chordate,
"Yunnanozoon" is similar to the form "Haikouella", which is almost certainly a chordate. Still, there are anatomical differences from "Haikouella", including a smaller stomach and much larger (1 mm) pharyngeal teeth. It is by no means certain whether Yunannozoon possessed features such as a heart, gills, etc., which are seen in well-preserved specimens of "Haikouella". "Yunnanozoon" somewhat resembles the Middle Cambrian "Pikaia" from the Burgess shale of British Columbia in Canada. Thirteen pairs of symmetrically arranged gonads have been identified, as have possible gill slits. However, some authors think that "Yunnanozoon" is closely related to the chordate "Haikouella" and that "Yunnanozoon" is probably a chordate rather than a hemichordate. A close relationship between "Yunnanozoon" and the taxon Vetulicolia has also been proposed.