| Olfactores | |
|---|---|
| |
| Example of Olfactores | |
Scientific classification 
| |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Olfactores Jefferies, 1991 |
| Subphyla | |
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.89
Anatomy of ancestral Olfactores
Some studies suggest that the ancestors of Appendicularia and Vertebrata were possibly sedentary-pelagic,101112 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
References
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) 39. Bibcode:2018BMCB...16...39D. doi:10.1186/s12915-018-0499-2. hdl:10261/163664. PMC 5899321. PMID 29653534.
- 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): 1–11. Bibcode:2012PalJ...46....1F. 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. pp. 94–127. doi:10.1002/9780470514160.ch7. ISBN 978-0-471-92961-1. PMID 1802652.
- 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. Bibcode:2023NatCo..14.3832N. doi:10.1038/s41467-023-39012-4. ISSN 2041-1723. PMC 10325964. PMID 37414759.
- 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.
{{cite journal}}: CS1 maint: DOI inactive as of July 2025 (link) - 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.