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Temporal range:
Cambrian Stage 3Present,
518–0 Ma[1] (Possible Ediacaran record, 557 Ma[2])
Example of Olfactores
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Subkingdom: Eumetazoa
Clade: ParaHoxozoa
Clade: Bilateria
Clade: Nephrozoa
Superphylum: Deuterostomia
Phylum: Chordata
Clade: Olfactores
Jefferies, 1991

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]

Olfactores hypothesis

While the hypothesis that Cephalochordata is a sister taxon to Craniata is of long standing and was once widely accepted[4]—likely influenced by significant tunicate morphological apomorphies from other chordates, with cephalochordates even being nicknamed ‘honorary vertebrates’[5]—studies since 2006 analyzing large sequencing datasets strongly support Olfactores as a clade.[6][7] The name Olfactores comes from Latin *olfactores ("smellers," from purposive supine olfactum of olfacio, "to smell," with plural masculine agentive nominalizing suffix -tores), due to the development of pharyngeal respiratory and sensory functions, in contrast with cephalochordates such as the lancelet which lack a respiratory system and specialized sense organs.[8]


  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.
  4. ^ Stach, Thomas (2008). "Chordate phylogeny and evolution: a not so simple three‐taxon problem". Journal of Zoology. 276 (2): 117–141. doi:10.1111/j.1469-7998.2008.00497.x.
  5. ^ Ax, P (2001). "Das System der Metazoa: ein Lehrbuch der phylogenetischen Systematik". ((cite journal)): Cite journal requires |journal= (help)
  6. ^ Delsuc, F (2006). "Tunicates and not cephalochordates are the closest living relatives of vertebrates" (PDF). Nature. 439 (7079): 965–968. Bibcode:2006Natur.439..965D. doi:10.1038/nature04336. PMID 16495997. S2CID 4382758.
  7. ^ Dunn, C.W. (2008). "Broad phylogenetic sampling improves resolution of the animal tree of life". Nature. 452 (7188): 745–749. Bibcode:2008Natur.452..745D. doi:10.1038/nature06614. PMID 18322464. S2CID 4397099.
  8. ^ Benton, M.J. (14 April 2000). Vertebrate Palaeontology: Biology and Evolution. Blackwell Publishing.
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