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A chordate (/ ˈ k ɔːr d eɪ t / KOR-dayt) is a deuterostomal bilaterian animal belonging to the phylum Chordata (/ k ɔːr ˈ d eɪ t ə / kor-DAY-tə).All chordates possess, at some point during their larval or adult stages, five distinctive physical characteristics (synapomorphies) that distinguish them from other taxa.
This article contains a list of all of the classes and orders that are located in the Phylum Chordata. The subphyla Tunicata and Vertebrata are in the unranked Olfactores clade, while the subphylum Cephalochordata is not. Animals in Olfactores are characterized as having a more advanced olfactory system than animals not in it.
Another feature present in both the Hemichordata and Chordata is pharyngotremy — the presence of spiracles or gill slits into the pharynx, which is also found in some primitive fossil echinoderms . [17] [18] A hollow nerve cord is found in all chordates, including tunicates (in the larval stage). Some hemichordates also have a tubular nerve cord.
The Cambrian chordates are an extinct group of animals belonging to the phylum Chordata that lived during the Cambrian, between 538 and 485 million years ago. The first Cambrian chordate known is Pikaia gracilens , a lancelet -like animal from the Burgess Shale in British Columbia , Canada.
Mammalia is a class of animal within the phylum Chordata. Mammal classification has been through several iterations since Carl Linnaeus initially defined the class. No classification system is universally accepted; McKenna & Bell (1997) and Wilson & Reader (2005) provide useful recent compendiums. [1]
The lancelets (/ ˈ l æ n s l ɪ t s, ˈ l ɑː n-/ LA(H)N-slits), also known as amphioxi (sg.: amphioxus / ˌ æ m f i ˈ ɒ k s ə s / AM-fee-OK-səs), consist of 32 described species of "fish-like" benthic filter feeding chordates [9] in the subphylum Cephalochordata, class Leptocardii, and family Branchiostomatidae.
A tunicate is an exclusively marine invertebrate animal, a member of the subphylum Tunicata (/ ˌ tj uː n ɪ ˈ k eɪ t ə / TEW-nih-KAY-tə).This grouping is part of the Chordata, a phylum which includes all animals with dorsal nerve cords and notochords (including vertebrates).
A hollow neural tube exists among some species (at least in early life), probably a primitive trait that they share with the common ancestor of chordata and the rest of the deuterostomes. [8] Hemichordates have a nerve net and longitudinal nerves, but no brain. [9] [10] Some species biomineralize in calcium carbonate. [11]