Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Yunnanozoon lividum ("Livid Animal of Yunnan") is a suspected chordate or hemichordate from the Lower Cambrian, Chengjiang biota of Yunnan province, China. Yunnanozoon is similar to the form Haikouella which is almost certainly a vertebrate. Still, there are anatomical differences from Haikouella, including a smaller stomach and much larger (1 mm) pharyngeal teeth. Yunannozoon is not known for sure to possess many features like heart, gills, etc. that are known from 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 phylum Vetulicolia has also been proposed.

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