''Yuyuanozoon magnificissimi'', from the
Cambrian Stage 3
Cambrian Stage 3 is the still unnamed third stage of the Cambrian. It succeeds Cambrian Stage 2 and precedes Cambrian Stage 4, although neither its base nor top have been formally defined. The plan is for its lower boundary to correspond approxima ...
Chengjiang lagerstatte, is the largest known
vetulicolia
Vetulicolia is a group of bilaterian marine animals encompassing several extinct species from the Cambrian, and possibly Ediacaran, periods. As of 2023, the majority of workers favor placing Vetulicolians in the stem group of the Chordata, but ...
n, an extinct species of marine animal, with specimens up to 20 cm in length compared to 5–14 cm for other vetulicolian species.
Etymology
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.
Description
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.
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.
Taxonomy
''Yuyuanozoon'' is a member of the
Didazoonidae. It was originally placed ''
incertae sedis
or is a term used for a taxonomy (biology), taxonomic group where its broader relationships are unknown or undefined. Alternatively, such groups are frequently referred to as "enigmatic taxa". In the system of open nomenclature, uncertainty ...
'' with in the phylum Vetulicolia,
then moved under the Vetulicolidae in a comprehensive review of the phylum, 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.
A 2024 study has found the Didazoonidae to be a paraphyletic grade of the vetulicolians closest to
crownward chordates
A chordate ( ) is a bilaterian animal belonging to the phylum Chordata ( ). All chordates possess, at some point during their larval or adult stages, five distinctive physical characteristics ( synapomorphies) that distinguish them from ot ...
as shown in this simplified cladogram:
[ ]
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:
See also
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Maotianshan shales
The Maotianshan Shales () are a series of Early Cambrian sedimentary deposits in the Chiungchussu Formation or Heilinpu Formation, famous for their '' Konservat Lagerstätten'', deposits known for the exceptional preservation of fossilized orga ...
References
Works cited
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Vetulicolia
Enigmatic prehistoric animal genera
Prehistoric chordate genera
Cambrian chordates
Cambrian genus extinctions
Cambrian animals of Asia
Maotianshan shales fossils
Fossil taxa described in 2001
{{Chordate-stub