Olfactores

Olfactores Temporal range: Cambrian Stage 3 – Present, 518–0  Ma [1] PreꞒ Ꞓ O S D C P T J K Pg N (Possible Ediacaran record, 557 Ma [2] )
Example of Olfactores
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Olfactores Jefferies, 1991
Subphyla
Tunicata Vertebrata ("Craniata")

Olfactores is a clade within the Chordata that comprises the Tunicata (Urochordata) and the Vertebrata (sometimes referred to as Craniata). ^[3] Olfactores represent the overwhelming majority of the phylum Chordata, as the Cephalochordata (with only 32 known species across 3 genera) ^[4] 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, gave rise to nostrils.

Etymology

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. ^[3]

Olfactores hypothesis

The long-standing Euchordata hypothesis that Cephalochordata is a sister taxon to Craniata was once widely accepted, ^[5] likely influenced by significant tunicate morphological apomorphies from other chordates, with cephalochordates even being nicknamed 'honorary vertebrates.' ^[6]

The name Olfactores was originally introduced in 1991 as part of the now-disproven calcichordate hypothesis. ^[7] However, studies since 2006 analyzing large sequencing datasets strongly support Olfactores as a clade. ^{[8] [9]}

Anatomy of ancestral Olfactores

Some studies suggest that the ancestors of Appendicularia and Vertebrata were possibly sedentary-pelagic, ^{[10] [11] [12]} although others recover a free-living chordate ancestor transitioning to free-living vertebrates without an intervening sedentary form. ^[13] A rudimentary neural crest is present in tunicates, implying its presence in the Olfactores ancestor also, as vertebrates have a true neural crest. ^[14]

References

1. Yang et al. 2018
2. Fedonkin et al. 2012
3. Benton 2000
4. Poss & Boschung 1996
5. Stach 2008
6. Ax 2001
7. Jeffries , p. 116, Fig. 15 caption harvnb error: no target: CITEREFJeffries (help)
8. Delsuc et al. 2006
9. Dunn et al. 2008
10. Delsuc et al. 2018
11. Nanglu et al. 2023
12. Martynov & Korshunova 2022
13. Mussini et al. 2024
14. York & McCauley 2020

Works cited

• Ax, P. (2001). Das System der Metazoa: ein Lehrbuch der phylogenetischen Systematik. Spektrum Akademischer Verlag. ISBN   978-3-437-30803-1.
• Benton, M.J. (14 April 2000). Vertebrate Palaeontology: Biology and Evolution. Blackwell Publishing.
• Delsuc, Frédéric; Brinkmann, Henner; Chourrout, Daniel; Philippe, Hervé (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.
• Delsuc, Frédéric; Philippe, Hervé; Tsagkogeorga, Georgia; Simion, Paul; Tilak, Marie-Ka; Turon, Xavier; López-Legentil, Susanna; Piette, Jacques; Lemaire, Patrick (2018-04-13). "A phylogenomic framework and timescale for comparative studies of tunicates". BMC Biology. 16 (39). doi: 10.1186/s12915-018-0499-2 . hdl: 10261/163664 . PMC   5899321 .
• Dunn, C.W.; Hejnol, A.; Matus, D.Q.; Pang, K.; Browne, W.E.; Smith, S.A.; Seaver, E.; Rouse, G.W.; Obst, M.; Edgecombe, G.D.; Sørensen, M.V.; Haddock, S.H.D.; Schmidt-Rhaesa, A.; Okusu, A.; Kristensen, R.M.; Wheeler, W.C.; Martindale, M.Q.; Giribet, G. (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.
• 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.
• Jeffries, R. P. S. (1991). "Two types of bilateral symmetry in the Metazoa: chordate and bilaterian". In Bock, Gregory R.; Marsh, Joan (eds.). Biological Asymmetry and Handedness. Ciba Foundation Symposium. John Wiley and Sons. doi:10.1002/9780470514160.ch7.
• Martynov, Alexander V.; Korshunova, Tatiana A. (2022-08-11). "Renewed perspectives on the sedentary-pelagic last common bilaterian ancestor". Contributions to Zoology. 91 (4–5): 285–352. doi:10.1163/18759866-bja10034. ISSN   1875-9866.
• 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. Bibcode:2024CBio...34.2980M. doi: 10.1016/j.cub.2024.05.026 . hdl: 10141/623098 . PMID   38866005.
• Nanglu, Karma; Lerosey-Aubril, Rudy; Weaver, James C.; Ortega-Hernández, Javier (2023-07-06). "A mid-Cambrian tunicate and the deep origin of the ascidiacean body plan". Nature Communications. 14 (1): 3832. doi:10.1038/s41467-023-39012-4. ISSN   2041-1723. PMC   10325964 .
• Poss, Stuart G.; Boschung, Herbert T. (1996). "Lancelets (cephalochordata: Branchiostomattdae): How Many Species Are Valid?". Israel Journal of Zoology. 42 (sup1): S13 –S66. doi:10.1080/00212210.1996.10688872 (inactive 2 July 2025). ISSN   0021-2210.
• 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 .
• 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.
• 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.