Yuyuanozoon

The generic name translates as "Animal of Yu Yuan," Yu Yuan being an ancient name for Chengjiang County. The specific name, magnificissimi, translates as "of the most magnificent one," in reference to the great size of the holotype.{{harvnb|Chen|Feng|Zhu|Ma|2003|page=282}}

Its body is non-biomineralized and consists of an elongate ovoid anterior section, with a segmented posterior section roughly one-third of the width and half the length of the anterior. The anterior opening is wide, with a narrow, raised circumventing rim 5 mm posterior to the opening. The anterior section is divided into six subdivisions by five circumventing lines, with gill openings placed symmetrically on each side, coinciding with the lines.{{harvnb|Li|Williams|Gabbott|Chen|2018|pages=1085–1086}} In the holotype, gill filaments are seen growing from the posterior side of the gill bars, but no filaments have been seen on the three more recently-examined specimens.

The posterior region consists of seven segments, each of which has five to six annulations (as also seen in Didazoon. It is more cylindrical than the posterior sections of other vetulicolians.

Yuyuanozoon is a member of the Didazoonidae. It was originally placed incertae sedis with in the phylum Vetulicolia, then moved under the Vetulicolidae in a comprehensive review of the phylum,{{harvnb|Aldridge|Hou|Siveter|Siveter|2007|142–145}} and most recently reassigned to the Didazoonidae based on additional specimens that clearly show the details of the anterior opening as well as annulations on each posterior segment.{{harvnb|Li|Williams|Gabbott|Chen|2018|page=1082}}

A 2024 study has found the Didazoonidae to be a paraphyletic grade of the vetulicolians closest to crownward chordates as shown in this simplified cladogram:{{harvnb|Mussini|Smith|Vinther|Rahman|2024|pages=6–7}} {{small|(Note: The cladogram is simplified using the definition of Vetulicolidae from Li et al. 2018, cited elsewhere on this page)}}

{{Clade|style=font-size:85%;line-height:85%

|label1=Chordata

|sublabel1={{small|(total group)}}

|1={{Clade

|1=Banffia†

|2=Heteromorphus†

|3={{Clade

|1=Skeemella†

|2={{Clade

|1=Nesonektris†

|2={{Clade

|1=Vetulicolidae†

|2={{Clade

|grouplabel1={{clade labels |bar1=indigo |label1="Didazoonidae"}}

|1=Didazoon† |barbegin1=indigo

|2=Pomatrum† |bar2=indigo

|3=Yuyuanozoon† |barend3=indigo

|4={{Clade

|1=Yunnanozoon†

|2={{Clade

|1=Cathaymyrus†

|2=Pikaia†

|3=Chordata
{{small|(crown group)}}

}} }} }} }} }} }} }} }}

An earlier study in 2014 placed vetulicolians as the sister-group to tunicates, but was unable to resolve any relationships among vetulicolians as a group:{{harvnb|García-Bellido|Lee|Edgecombe|Jago|2014|page=9}}

{{Clade|style=font-size:85%;line-height:85%

|label1=Vetulicolia†

|1={{Clade

|grouplabel4={{clade labels |bar1=indigo |label1="Didazoonidae"}}

|1=Vetulicola†

|2=Beidazoon†

|3=Ooedigera†

|4=Pomatrum† / Xidazoon† |barbegin4=indigo

|5=Didazoon† |bar5=indigo

|6=Yuyuanozoon† |barend6=indigo

|7=Banffia†

|8=Heteromorphus†

|9=Nesonektris†

}}

|2=Tunicata

}}

{{Portal|Paleontology}}

• Maotianshan shales

{{reflist}}

{{refbegin}}

• {{cite journal |last1=Aldridge |first1=Richard J. |last2=Hou |first2=Xian-guang |last3=Siveter |first3=David J. |last4=Siveter |first4=Derek J. |last5=Sarah E. |first5=Gabbott |year=2007 |title=The systematics and phylogenetic relationships of vetulicolians |journal=Palaeontology |volume=50 |pages=131–168 |doi=10.1111/j.1475-4983.2006.00606.x |s2cid=85722738}}
• {{cite journal|last1=Chen |first1=Ailin |last2=Feng |first2=Hongzhen |last3=Zhu |first3=Maoyan |last4=Ma |first4=Dongsheng |last5=Li |first5=Ming |year=2003 |title=A New Vetulicolian from the Early Cambrian Chengjiang Fauna in Yunnan of China |journal=Acta Geologica Sinica |volume=77 |issue=3 |pages=281–287 |s2cid=128895860 |doi=10.1111/j.1755-6724.2003.tb00742.x}}
• {{cite journal|last1=García-Bellido |first1=Diego C. |last2=Lee |first2=Michael S. Y. |last3=Edgecombe |first3=Gregory D. |last4=Jago |first4=James B. |last5=Gehling |first5=James G. |last6=Paterson |first6=John R. |year=2014 |title=A new vetulicolian from Australia and its bearing on the chordate affinities of an enigmatic Cambrian group |journal=BMC Evolutionary Biology |volume=14 |page=214 |doi=10.1186/s12862-014-0214-z |pmc=4203957 |pmid=25273382 |doi-access=free }}
• {{cite journal|last1=Li |first1=Yujing |last2=Williams |first2=Mark |last3=Gabbott |first3=Sarah E. |last4=Chen |first4=Ailen |last5=Cong |first5=Peiyun |last6=Hou |first6=Xianguang |title=The enigmatic metazoan Yuyuanozoon magnificissimi from the early Cambrian Chengjiang Biota, Yunnan Province, South China |journal=Journal of Paleontology |volume=92 |number=6 |year=2018 |pages=1081–1091 |doi=10.1017/jpa.2018.18}}
• {{cite journal |last1=Mussini |first1=G. |last2=Smith |first2=M. P. |last3=Vinther |first3=J. |last4=Rahman |first4=I. A. |last5=Murdock |first5=D. J. E. |last6=Harper |first6=D. A. T. |last7=Dunn |first7=F. S. |title=A new interpretation of Pikaia reveals the origins of the chordate body plan |journal=Current Biology |date=2024 |volume=34 |issue=13 |pages=2980–2989.e2 |doi=10.1016/j.cub.2024.05.026 |doi-access=free |pmid=38866005 }}

{{refend}}

{{Vetulicolia}}

{{Taxonbar|from=Q3573305}}

Category:Vetulicolia

Category:Enigmatic prehistoric animal genera

Category:Prehistoric chordate genera

Category:Cambrian chordates

Category:Cambrian genus extinctions

Category:Cambrian animals of Asia

Category:Maotianshan shales fossils

Category:Fossil taxa described in 2001

{{Chordate-stub}}