Didazoonidae

Didazoonidae Temporal range: Cambrian Stage 3 PreꞒ Ꞓ O S D C P T J K Pg N
Didazoon haoae Pomatrum ventralis Yuyuanozoon magnificissimi Artists' reconstructions of Didazoonids
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Clade?:	† Vetulicolia
Class:	† Vetulicolida
Order:	† Vetulicolata
Family:	† Didazoonidae Shu and Han in Shu et al. 2001
Type genus
† Didazoon Shu and Han in Shu et al. 2001
Genera
† Didazoon Shu and Han in Shu et al. 2001 † Pomatrum Luo and Hu, in Luo et al. 1999 † Yuyuanozoon Chen, Feng and Zhu in Chen et al. 2003 ? † Nesonektris García-Bellido et al. 2014

Didazoonidae is a vetulicolian family within the order Vetulicolata. It is characterized by a relatively thin-walled, non-biomineralized body and a large, round anterior opening surrounded by an oral disc. ^{[1] [2]} It may be paraphyletic, ^[3] even if the phylum Vetulicolia is monophyletic. ^[4]

Description

Didazoonids have an ovoid to subquadrate anterior section divided into six subdivisions marked by five circumventing lines perpendicular to the body axis. Cowl-shaped lateral pouches appear along each side of the anterior section, coincident with the five dividing lines. The anterior opening is large, round, and surrounded by a circumventing oral disc. The posterior section has seven segments, which in some species each carry up to six annulations. ^[2]

Taxonomy

Didazoonidae was erected to group Didazoon . Xidazoon . and Pomatrum , although Xidazoon has since been shown to be a junior synonym of Pomatrum. ^[1] Yuyuanozoon was moved to the Didazoonidae after additional specimens illuminated more details of the anterior opening and posterior segment annulations. ^[5]

Nesonektris has also been assigned to Didazoonidae by some workers, ^[6] but this has not been widely accepted. ^{[7] [8]}

A 2024 study has found the Didazoonidae (without Nesonektris) to be a paraphyletic grade of the vetulicolians closest to crownward chordates as shown in this simplified cladogram: ^[3]

Chordata	Banffia † Heteromorphus † Skeemella † Nesonektris † Vetulicolidae† Didazoon † "Didazoonidae" Pomatrum † Yuyuanozoon † Yunnanozoon † Cathaymyrus † Pikaia † Chordata (crown group)
(total 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: ^[4]

Vetulicolia†	Vetulicola † Beidazoon † Ooedigera † Pomatrum † / Xidazoon † "Didazoonidae" Didazoon † Yuyuanozoon † Banffia † Heteromorphus † Nesonektris †
	Tunicata

References

1. Aldridge et al. 2007 , pp. 145–146
2. Li et al. 2018 , p. 1085(Note: This paper uses different terminology for vetulicolian anatomy explained on page 1082; this page uses the more common terms regardless of source)
3. Mussini et al. 2024 , pp. 6–7(Note: The cladogram is simplified using the definition of Vetulicolidae from Li et al. 2018, cited elsewhere on this page)
4. García-Bellido et al. 2014 , p. 9
5. Li et al. 2018 , p. 1082
6. Li et al. 2018 , p. 1084
7. "†Nesonektris García-Bellido et al. 2014". Paleobiology Database. Retrieved December 8, 2024.
8. "†family Didazoonidae Shu and Han 2001". Paleobiology Database. Retrieved December 8, 2024.

Works cited

• Aldridge, Richard J.; Hou, Xian-guang; Siveter, David J.; Siveter, Derek J.; Sarah E., Gabbott (2007). "The systematics and phylogenetic relationships of vetulicolians". Palaeontology. 50: 131–168. doi:10.1111/j.1475-4983.2006.00606.x. S2CID   85722738.
• Chen, Ailin; Feng, Hongzhen; Zhu, Maoyan; Ma, Dongsheng; Li, Ming (2003). "A New Vetulicolian from the Early Cambrian Chengjiang Fauna in Yunnan of China". Acta Geologica Sinica. 77 (3): 281–287. doi:10.1111/j.1755-6724.2003.tb00742.x. S2CID   128895860.
• 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. hdl: 2381/41417 .
• 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 . hdl: 10141/623098 . 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.