Didazoon

Didazoon; Temporal range: Cambrian Stage 3 PreꞒ Ꞓ O S D C P T J K Pg N
	Fossils
	Restoration
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Clade?:	†Vetulicolia
Class:	†Vetulicolida
Order:	†Vetulicolata
Family:	†Didazoonidae
Genus:	†Didazoon; Shu & Han, 2001
Species:	†D. haoae
Binomial name
	†Didazoon haoae; Shu & Han, 2001

Didazoon haoae is an extinct species of vetulicolid vetulicolian described by Shu, et al. based on fossils found in the Qiongzhusi (Chiungchussu) Formation, Yu'anshan Member (Eoredlichia zone), Lower Cambrian, in the Dabanqiao area (Kunming), about 60 km northwest of Chengjiang, China.^[1]

Etymology

"Dida" abbreviates (in Chinese) the China University of Geosciences.^[2]

Description

The fossils show that the body of the animal was covered in a thin, flexible cuticle. The anterior part of the body was divided into six segments, with fairly broad membranes separating the segments, and the posterior part of the body was divided into seven segments. The constriction between the anterior and posterior parts of the animal shows creasing, and the authors hypothesize that it was quite flexible. The fossils are interpreted as showing a large anterior opening, presumably a mouth, a spacious anterior cavity, an alimentary canal, possibly voluminous in the anterior section, and a narrow intestine in the posterior section, straight or coiled (in one specimen). There are five structures on each side of the anterior portion that the authors interpret as gills. Narrow strands towards the lateral margins, sometimes branched, may represent vascular tissue. The authors also identify a dark strand on the lower interior surface of the anterior section, which they speculate is an endostyle.^[1]

Taxonomy

Didazoon is the type genus of the Didazoonidae, which one 2024 study has found to be a paraphyletic grade of the vetulicolians closest to crownward chordates as shown in this simplified cladogram,^[3] which labels Vetulicolidae based on a 2018 phylogeny^[4] and Didazoonidae based on the Paleobiology Database:^[5]

Chordata

Banffia†

Heteromorphus†

Skeemella†

Nesonektris†

Vetulicolidae†

Didazoon†

"Didazoonidae"

Pomatrum†

Yuyuanozoon†

Yunnanozoon†

	Cathaymyrus†

	Pikaia†

	Chordata (crown group)

(total group)

An earlier study in 2014 place vetulicolians as the sister-group to tunicates, but was unable to resolve any relationships among vetulicolians as a group:^[6]

Vetulicolia†

	Vetulicola†

	Beidazoon†

	Ooedigera†

	Pomatrum† / Xidazoon†	"Didazoonidae"

	Didazoon†

	Yuyuanozoon†

	Banffia†

	Heteromorphus†

	Nesonektris†

Tunicata

References

^ ^a ^b Shu et al. 2001
^ Shu et al. 2001, p. 419 (Note: it is unclear from the source whether the China University of Geosciences (Wuhan) or China University of Geosciences (Beijing) is being referenced)
^ Mussini et al. 2024, pp. 6–7
^ Li et al. 2018, pp. 1083–1084
^ "†family Didazoonidae Shu and Han 2001". Paleobiology Database. Retrieved December 8, 2024.
^ García-Bellido et al. 2014, p. 9

Works cited

García-Bellido, Diego C.; Lee, Michael S. Y.; Edgecombe, Gregory D.; Jago, James B.; Gehling, James G.; Paterson, John R. (2014). "A new vetulicolian from Australia and its bearing on the chordate affinities of an enigmatic Cambrian group". BMC Evolutionary Biology. 14: 214. doi:10.1186/s12862-014-0214-z. PMC 4203957. PMID 25273382.
Li, Yujing; Williams, Mark; Gabbott, Sarah E.; Chen, Ailen; Cong, Peiyun; Hou, Xianguang (2018). "The enigmatic metazoan Yuyuanozoon magnificissimi from the early Cambrian Chengjiang Biota, Yunnan Province, South China". Journal of Paleontology. 92 (6): 1081–1091. doi:10.1017/jpa.2018.18.
Mussini, G.; Smith, M. P.; Vinther, J.; Rahman, I. A.; Murdock, D. J. E.; Harper, D. A. T.; Dunn, F. S. (2024). "A new interpretation of Pikaia reveals the origins of the chordate body plan". Current Biology. 34 (13): 2980–2989.e2. doi:10.1016/j.cub.2024.05.026. PMID 38866005.
Shu, D. G.; Conway Morris, S.; Han, J.; Chen, L.; Zhang, X. L.; Zhang, Z. F.; Liu, H. Q.; Li, Y.; Liu, J. N. (November 22, 2001). "Primitive deuterostomes from the Chengjiang Lagerstätte (Lower Cambrian, China)". Nature. 414 (6862): 419–424. Bibcode:2001Natur.414..419S. doi:10.1038/35106514. ISSN 0028-0836. PMID 11719797. S2CID 4345484.

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[Shu2001-1] Shu et al. 2001

[Shu2001basics-2] Shu et al. 2001, p. 419 (Note: it is unclear from the source whether the China University of Geosciences (Wuhan) or China University of Geosciences (Beijing) is being referenced)

[MussiniCladogram-3] Mussini et al. 2024, pp. 6–7

[Li2018-4] Li et al. 2018, pp. 1083–1084

[5] "†family Didazoonidae Shu and Han 2001". Paleobiology Database. Retrieved December 8, 2024.

[GB2014-6] García-Bellido et al. 2014, p. 9

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