Olfactores
Clade of animals comprising vertebrates and tunicates
From Wikipedia, the free encyclopedia
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.
Jefferies, 1991
| Olfactores | |
|---|---|
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| Example of Olfactores | |
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Olfactores Jefferies, 1991 |
| Subphyla | |
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]