Olfactores

Olfactores; Temporal range: ; Cambrian Stage 3–Present,; (Possible Ediacaran record, 557 Ma)
	Example of Olfactores
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Subkingdom:	Eumetazoa
Clade:	ParaHoxozoa
Clade:	Bilateria
Clade:	Nephrozoa
Superphylum:	Deuterostomia
Phylum:	Chordata
Clade:	Olfactores; Jefferies, 1991
Subgroups
	Tunicata; Vertebrata; †Zhongxiniscus;

Olfactores is a clade within the Chordata that comprises the Tunicata (Urochordata) and the Vertebrata (sometimes referred to as Craniata). Olfactores represent the overwhelming majority of the phylum Chordata, as the Cephalochordata are the only chordates not included in the clade. This clade is defined by a more advanced olfactory system which, in the immediate vertebrate generation, caused the appearance of nostrils.

A rudimentary neural crest is present in tunicates, implying its presence in the olfactores ancestor also, as vertebrates have a true neural crest.^[3] For this reason, they are also known as Cristozoa.^{[clarification needed]}

^ Yang, Chuan; Li, Xian-Hua; Zhu, Maoyan; Condon, Daniel J.; Chen, Junyuan (2018). "Geochronological constraint on the Cambrian Chengjiang biota, South China" (PDF). Journal of the Geological Society. 175 (4): 659–666. Bibcode:2018JGSoc.175..659Y. doi:10.1144/jgs2017-103. ISSN 0016-7649. S2CID 135091168.
^ Fedonkin, M. A.; Vickers-Rich, P.; Swalla, B. J.; Trusler, P.; Hall, M. (2012). "A new metazoan from the Vendian of the White Sea, Russia, with possible affinities to the ascidians". Paleontological Journal. 46: 1–11. doi:10.1134/S0031030112010042. S2CID 128415270.
^ York, Joshua R.; McCauley, David W. (2020). "The origin and evolution of vertebrate neural crest cells". Open Biology. 10 (1): 190285. doi:10.1098/rsob.190285. PMC 7014683. PMID 31992146.

[1] Yang, Chuan; Li, Xian-Hua; Zhu, Maoyan; Condon, Daniel J.; Chen, Junyuan (2018). "Geochronological constraint on the Cambrian Chengjiang biota, South China" (PDF). Journal of the Geological Society. 175 (4): 659–666. Bibcode:2018JGSoc.175..659Y. doi:10.1144/jgs2017-103. ISSN 0016-7649. S2CID 135091168.

[2] Fedonkin, M. A.; Vickers-Rich, P.; Swalla, B. J.; Trusler, P.; Hall, M. (2012). "A new metazoan from the Vendian of the White Sea, Russia, with possible affinities to the ascidians". Paleontological Journal. 46: 1–11. doi:10.1134/S0031030112010042. S2CID 128415270.

[3] York, Joshua R.; McCauley, David W. (2020). "The origin and evolution of vertebrate neural crest cells". Open Biology. 10 (1): 190285. doi:10.1098/rsob.190285. PMC 7014683. PMID 31992146.

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