''Yunnanozoon lividum'' (Yunnan + Greek ζῷον ''zôion'', ''lividum''; "livid animal of Yunnan") is an extinct species of possible

vertebrate Vertebrates () comprise all animal taxa within the subphylum Vertebrata () (chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, with c ...

chordate A chordate () is an animal of the phylum Chordata (). All chordates possess, at some point during their larval or adult stages, five synapomorphies, or primary physical characteristics, that distinguish them from all the other taxa. These fi ...

from the Lower Cambrian, Chengjiang biota of

Yunnan Yunnan , () is a landlocked province in the southwest of the People's Republic of China. The province spans approximately and has a population of 48.3 million (as of 2018). The capital of the province is Kunming. The province borders the C ...

province, China. It is thought of as a deuterostome suspected of being either a

hemichordate Hemichordata is a phylum which consists of triploblastic, enterocoelomate, and bilaterally symmetrical marine deuterostome animals, generally considered the sister group of the echinoderms. They appear in the Lower or Middle Cambrian and includ ...

. In 2022, a study reanalyzed fossils of ''Yunnanozoon'' and found it to be one of the earliest members of the vertebrate family tree. ''Yunnanozoon'' is similar to the form ''

Haikouella ''Haikouella'' is an agnathan chordate from the Lower Cambrian Maotianshan Shales of Chengjiang County in Yunnan Province, China. An analysis in 2015 placed ''Haikouella'' as a junior synonym of ''Yunnanozoon,'' another Maotianshan shale Cambrian ...

'', which is almost certainly a chordate. Still, there are anatomical differences from ''Haikouella'', including a smaller

stomach The stomach is a muscular, hollow organ in the gastrointestinal tract of humans and many other animals, including several invertebrates. The stomach has a dilated structure and functions as a vital organ in the digestive system. The stomach i ...

and much larger (1 mm)

pharyngeal teeth Pharyngeal teeth are teeth in the pharyngeal arch of the throat of cyprinids, suckers, and a number of other fish species otherwise lacking teeth.heart The heart is a muscular organ in most animals. This organ pumps blood through the blood vessels of the circulatory system. The pumped blood carries oxygen and nutrients to the body, while carrying metabolic waste such as carbon dioxide to t ...

gill A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they are ...

s, etc., which are seen in well-preserved specimens of ''

''. ''Yunnanozoon'' somewhat resembles the Middle Cambrian ''

Pikaia ''Pikaia gracilens'' is an extinct, primitive chordate animal known from the Middle Cambrian Burgess Shale of British Columbia. Described in 1911 by Charles Doolittle Walcott as an annelid, and in 1979 by Harry B. Whittington and Simon Conway ...

'' from the

Burgess shale The Burgess Shale is a fossil-bearing deposit exposed in the Canadian Rockies of British Columbia, Canada. It is famous for the exceptional preservation of the soft parts of its fossils. At old (middle Cambrian), it is one of the earliest fo ...

British Columbia British Columbia (commonly abbreviated as BC) is the westernmost province of Canada, situated between the Pacific Ocean and the Rocky Mountains. It has a diverse geography, with rugged landscapes that include rocky coastlines, sandy beaches, ...

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 VetulicoliaThe taxon name, Vetulocolia, is derived from the type genus, ''Vetulicola'', which is a compound Latin word composed of ''vetuli'' "old" and ''cola'' "inhabitant". is a taxon (either phylum or subphylum in rank) encompassing several ex ...

has also been proposed. An analysis in 2015 placed ''Haikouella'' as a junior synonym of ''Yunnanozoon.''

References

External links

* A picture can be found at https://web.archive.org/web/20030511135309/http://www.gs-rc.org:80/repo/repoe.htm Maotianshan shales fossils Enigmatic deuterostome taxa Cambrian chordates Fossil taxa described in 1995 Prehistoric chordate genera Chordates Cambrian genus extinctions {{cambrian-animal-stub

See also

References

External links