Chordate
1
Chordate
Chordata
Temporal range: Early Cambrian – Recent, 540–0Ma
The X-ray tetra (Pristella maxillaris) is one of the few chordates with a visible backbone. The spinal cord is housed within its
backbone.
Scientific classification
Kingdom:
Animalia
Superphylum:
Deuterostomia
Phylum:
Chordata
Haeckel, 1874
Classes
See below
Chordates, members of the phylum Chordata, are deuterostome animals possessing a notochord, a hollow dorsal
nerve cord, pharyngeal slits, an endostyle, and a post-anal tail for at least some period of their life cycles.
Taxonomically, the phylum includes the subphyla Vertebrata, including mammals, fish, amphibians, reptiles, birds;
Tunicata, including salps and sea squirts; and Cephalochordata, comprising the lancelets.
The phylum Hemichordata including the acorn worms has been presented as a fourth chordate subphylum, but it now
is usually treated as a separate phylum. It, along with the echinoderm phylum, including starfish, sea urchins, and sea
cucumbers and their kin, are the chordates' closest relatives. Primitive chordates are known from at least as early as
the Cambrian explosion.
There are more than 75,000 living species of chordates, about half of which are bony fish of the class osteichthyes.
The world's largest animal, the blue whale, and fastest animal, the peregrine falcon, are chordates, as are humans.[1]
Chordate
Overview of affinities
Tunicate larvae have both a notochord and a nerve cord which are lost in adulthood. Cephalochordates have a
notochord and a nerve cord (but no brain or specialist sensory organs) and a very simple circulatory system.
Craniates are the only subphylum whose members have skulls. In all craniates except for hagfish, the dorsal hollow
nerve cord is surrounded with cartilaginous or bony vertebrae and the notochord is generally reduced; hence, hagfish
are not universally regarded as vertebrates, though recent DNA comparisons suggest that they are in fact vertebrates.
The chordates and two sister phyla, the Hemichordata and the Echinodermata, make up the deuterostomes, one of the
two superphyla that encompass all fairly complex animals. An article by Nakano et al. demonstrates that the
Xenoturbellida are not deuterostomes.
Attempts to work out the evolutionary relationships of the chordates have produced several hypotheses. The current
consensus is that chordates are monophyletic, meaning that the Chordata include all and only the descendants of a
single common ancestor which is itself a chordate, and that craniates' nearest relatives are cephalochordates. All of
the earliest chordate fossils have been found in the Early Cambrian Chengjiang fauna, and include two species that
are regarded as fish, which implies they are vertebrates. Because the fossil record of chordates is poor, only
molecular phylogenetics offers a reasonable prospect of dating their emergence. However, the use of molecular
phylogenetics for dating evolutionary transitions is controversial.
It has also proved difficult to produce a detailed classification within the living chordates. Attempts to produce
evolutionary "family trees" give results that differ from traditional classes because several of those classes are not
monophyletic. As a result, vertebrate classification is in a state of flux.
For a recent concise review of chordate relationships, see Holland, N. D. 2005, Chordates. Curr. Biol. 15:
R911-R914.
Origin of name
Although the name Chordata is often attributed to William Bateson (1885), it was already in prevalent use in by
1880. Ernst Haeckel described a taxon comprising tunicates, cephalochordates, and vertebrates in 1866. Though he
used the German vernacular form, it is allowed under the ICZN code because of its subsequent latinization.
Definition
Anatomy of the cephalochordate Amphioxus. Bolded items are components of all chordates at some point in their
lifetimes, and distinguish them from other phyla.
Chordates form a phylum of creatures that are based on a bilateral body plan,[2] and is defined by having at some
stage in their lives all of the following:
• A notochord, in other words a fairly stiff rod of cartilage that extends along the inside of the body. Among the
vertebrate sub-group of chordates the notochord develops into the spine, and in wholly aquatic species this helps
the animal to swim by flexing its tail.
• A dorsal neural tube. In fish and other vertebrates this develops into the spinal cord, the main communications
trunk of the nervous system.
• Pharyngeal slits. The pharynx is the part of the throat immediately behind the mouth. In fish the slits are modified
to form gills, but in some other chordates they are part of a filter-feeding system that extracts particles of food
from the water in which the animals live.
• Post-anal tail. A muscular tail that extends backwards behind the anus.
• An endostyle. This is a groove in the ventral wall of the pharynx. In filter-feeding species it produces mucus to
gather food particles, which helps in transporting food to the esophagus. It also stores iodine, and may be a
precursor of the vertebrate thyroid gland.
2
Chordate
Subdivisions
Craniata
Craniates, one of the three subdivisions of chordates, have distinct
skulls - including hagfish, which have no vertebrae. Michael J. Benton
comments, "craniates are characterized by their heads, just as
chordates, or possibly all deuterostomes, are by their tails".
Most are vertebrates, in which the notochord is replaced by the spinal
column, which consists of a series of bony or cartilaginous cylindrical
vertebrae, generally with neural arches that protect the spinal cord and
with projections that link the vertebrae. Hagfish have incomplete
braincases and no vertebrae, and are therefore not regarded as
Craniate: Hagfish
vertebrates, but as members of the craniates, the group from which
vertebrates are thought to have evolved. The position of lampreys is ambiguous. They have complete braincases and
rudimentary vertebrae, and therefore may be regarded as vertebrates and true fish. However, molecular
phylogenetics, which uses biochemical features to classify organisms, has produced both results that group them
with vertebrates and others that group them with hagfish.
Urochordata: tunicates
Most tunicates appear as adults in two major forms, both of which are
soft-bodied filter-feeders that lack the standard features of chordates:
"sea squirts" are sessile and consist mainly of water pumps and
filter-feeding apparatus; salps float in mid-water, feeding on plankton,
and have a two-generation cycle in which one generation is solitary
and the next forms chain-like colonies. However, all tunicate larvae
have the standard chordate features, including long, tadpole-like tails;
they also have rudimentary brains, light sensors and tilt sensors. The
third main group of tunicates, Appendicularia (also known as
Larvacea) retain tadpole-like shapes and active swimming all their
Tunicates: sea squirts
lives, and were for a long time regarded as larvae of sea squirts or
salps. The etymology of the term Urochorda(ta) (Balfour 1881) is from
the ancient Greek οὐρά (oura, "tail") + Latin chorda ("cord"), because the notochord is only found in the tail.[3] The
term Tunicata (Lamarck 1816) is recognised as having precedence and is now more commonly used.
3
Chordate
4
Cephalochordata: lancelets
Cephalochordates are small, "vaguely fish-shaped" animals that lack
brains, clearly defined heads and specialized sense organs. These
burrowing filter-feeders comprise the earliest-branching chordate
sub-phylum.
Closest nonchordate relatives
Cephalochordate: Lancelet
Hemichordates
Hemichordates ("half (½) chordates") have some features similar to
those of chordates: branchial openings that open into the pharynx and
look rather like gill slits; stomochords, similar in composition to
notochords, but running in a circle round the "collar", which is ahead
of the mouth; and a dorsal nerve cord — but also a smaller ventral
nerve cord.
There are two living groups of hemichordates. The solitary
enteropneusts, commonly known as "acorn worms", have long
proboscises and worm-like bodies with up to 200 branchial slits, are up
Hemichordate: Acorn worm
to 2.5 metres (8.2 ft) long, and burrow though seafloor sediments.
Pterobranchs are colonial animals, often less than 1 millimetre (0.039 in) long individually, whose dwellings are
interconnected. Each filter feeds by means of a pair of branched tentacles, and has a short, shield-shaped proboscis.
The extinct graptolites, colonial animals whose fossils look like tiny hacksaw blades, lived in tubes similar to those
of pterobranchs.
Echinoderms
Echinoderms differ from chordates and their other relatives in
three conspicuous ways: they possess bilateral symmetry as larvae
and in adulthood they have radial symmetry, meaning their body
pattern is shaped like a wheel; they have tube feet; and their bodies
are supported by skeletons made of calcite, a material not used by
chordates. Their hard, calcified shells keep their bodies well
protected from the environment, and these skeletons enclose their
bodies, but are also covered by thin skins. The feet are powered by
another unique feature of echinoderms, a water vascular system of
Echinoderm: starfish
canals that also functions as a "lung" and are surrounded by
muscles that act as pumps. Crinoids look rather like flowers, and
use their feather-like arms to filter food particles out of the water; most live anchored to rocks, but a few can move
very slowly. Other echinoderms are mobile and take a variety of body shapes, for example starfish, sea urchins and
sea cucumbers.
Chordate
5
Origins
The majority of animals more complex than jellyfish and other Cnidarians are split into two groups, the protostomes
and deuterostomes, the latter of which contains chordates. It seems very likely the 555 [4] million-year-old
Kimberella was a member of the protostomes. If so, this means the protostome and deuterostome lineages must have
split some time before Kimberella appeared — at least 558 [5] million years ago, and hence well before the start of
the Cambrian 541 [6] million years ago. The Ediacaran fossil Ernietta, from about 549 to 543 [7] million years ago,
may represent a deuterostome animal.[8]
Fossils of one major deuterostome group, the echinoderms (whose
modern members include starfish, sea urchins and crinoids), are quite
common from the start of the Cambrian, 542 [10] million years ago.
The Mid Cambrian fossil Rhabdotubus johanssoni has been interpreted
[9]
Haikouichthys, from about 518
million years
as a pterobranch hemichordate. Opinions differ about whether the
ago in China, may be the earliest known fish.
Chengjiang fauna fossil Yunnanozoon, from the earlier Cambrian, was
a hemichordate or chordate. Another fossil, Haikouella lanceolata, also
from the Chengjiang fauna, is interpreted as a chordate and possibly a craniate, as it shows signs of a heart, arteries,
gill filaments, a tail, a neural chord with a brain at the front end, and possibly eyes — although it also had short
tentacles round its mouth. Haikouichthys and Myllokunmingia, also from the Chengjiang fauna, are regarded as fish.
Pikaia, discovered much earlier (1911) but from the Mid Cambrian Burgess Shale (505 Ma), is also regarded as a
primitive chordate. On the other hand fossils of early chordates are very rare, since non-vertebrate chordates have no
bones or teeth, and only one has been reported for the rest of the Cambrian.
Xenoturbellida
Hemichordates
Echinoderms
Deuterostomes
Cephalochordates
Chordates
Tunicates (Urochordates)
Craniates
A consensus family tree of the chordates
The evolutionary relationships between the chordate groups and between chordates as a whole and their closest
deuterostome relatives have been debated since 1890. Studies based on anatomical, embryological, and
paleontological data have produced different "family trees". Some closely linked chordates and hemichordates, but
that idea is now rejected. Combining such analyses with data from a small set of ribosome RNA genes eliminated
some older ideas, but open the possibility that tunicates (urochordates) are "basal deuterostomes", surviving
members of the group from which echinoderms, hemichordates and chordates evolved. Some researchers believe
that, within the chordates, craniates are most closely related to cephalochordates, but there are also reasons for
regarding tunicates (urochordates) as craniates' closest relatives. One other phylum, Xenoturbellida, has been thought
for a while to be basal within the deuterostomes, closer to the original deuterostomes than to the chordates,
Chordate
6
echinoderms and hemichordates.[] But an article by Nakano et al. ("Xenoturbella bocki exhibits direct development
with similarities to Acoelomorpha", Nature Communications, 2013; 4: 1537 DOI: 10.1038/ncomms2556)
demonstrates that the Xenoturbellida are not deuterostomes.
Since chordates have left a poor fossil record, attempts have been made to calculate the key dates in their evolution
by molecular phylogenetics techniques - by analyzing biochemical differences, mainly in RNA. One such study
suggested deuterostomes arose before 900 [11] million years ago and the earliest chordates around 896 [12] million
years ago. However, molecular estimates of dates often disagree with each other and with the fossil record, and their
assumption that the molecular clock runs at a known constant rate has been challenged.
Classification
Taxonomy
Traditionally, Cephalochordata and Craniata were grouped into the
proposed clade "Euchordata", which would have been the sister group
to Tunicata/Urochordata. More recently, Cephalochordata has been
thought of as a sister group to the "Olfactores", which includes the
craniates and tunicates. The matter is not yet settled.
The following schema is from the third edition of Vertebrate
Palaeontology.[13] The invertebrate chordate classes are from Fishes of
the World. While it is structured so as to reflect evolutionary
relationships (similar to a cladogram), it also retains the traditional
ranks used in Linnaean taxonomy.
A skeleton of the blue whale, the world's largest
animal, outside the Long Marine Laboratory at
the University of California, Santa Cruz
• Phylum Chordata
• Subphylum Tunicata (Urochordata) — (tunicates; 3,000
species)
• Class Ascidiacea (sea squirts)
• Class Thaliacea (salps)
• Class Appendicularia (larvaceans)
• Class Sorberacea
• Subphylum Cephalochordata (Acraniata) — (lancelets; 30
species)
• Class Leptocardii (lancelets)
• Subphylum Vertebrata (Craniata) (vertebrates — animals with
backbones; 57,674 species)
A peregrine falcon, the world's fastest animal
• Infraphylum incertae sedis
• Superclass 'Agnatha' paraphyletic (jawless vertebrates; 100+ species)
• Class Myxini (hagfish; 65 species)
• Class Petromyzontida or Hyperoartia (lampreys)
• Class †Conodonta
• Class †Pteraspidomorphi
• Class †Thelodonti
• Class †Anaspida
• Class †Cephalaspidomorphi
• Infraphylum Gnathostomata (jawed vertebrates)
Chordate
7
• Superclass incertae sedis
• Class †Placodermi (Paleozoic armoured forms)
• Class Chondrichthyes (cartilaginous fish; 900+ species)
• Class †Acanthodii (Paleozoic "spiny sharks")
• Superclass Osteichthyes (bony fish; 30,000+ species)
• Class Actinopterygii (ray-finned fish; about 30,000 species)
• Class Sarcopterygii (lobe-finned fish: 8 species)
• Superclass Tetrapoda (four-limbed vertebrates; 28,000+ species)
•
•
•
•
•
Class Amphibia (amphibians; 6,000 species)
Class Reptilia (reptiles; 9,000+ species)
Class †Synapsida (synapsids; 4,000+ species)
Class Aves (birds; 10,000-12,000 species, nearly 22,000 subspecies)
Class Mammalia (mammals; 5,700+ species)
Phylogeny
Chordates
the Chordate phylum. Lines show probable evolutionary relationships, including extinct taxa, which are denoted with a dagger, †. Some are invertebrates. The positions
) of the Lancelet, Tunicate, and Craniata clades are as reported in the scientific journal Nature.
Chordate
8
alochordataAmphioxus
Appendicularia (formerly Larvacea)
Tunicata Thaliacea
Ascidiacea
Myxini
Conodonta†
Cephalaspidomorphi†
Hyperoartia (Petromyzontida)
Pteraspidomorphi†
Placodermi†
Chondrichthyes
Acanthodii†
Actinopterygii
factores
Amphibia
Craniata
Vertebrata
Mammalia
Gnathostomata
Teleostomi
Osteichthyes
Sarcopterygii void Tetrapoda Amniota
Lepidosauromor
void (lizards, snakes,
tuatara, and their
extinct relatives)
Sauropsida
Archosauromorp
(crocodiles, bird
their extinct rela
Chordate
References
[1] AccessScience.com (http:/ / www. accessscience. com/ abstract. aspx?id=133700& referURL=http:/ / www. accessscience. com/ content.
aspx?id=133700). Retrieved 23 December 2012.
[2] "Classifications of organisms in hierarchical systems were in use by the seventeenth and eighteenth centuries. Usually organisms were
grouped according to their morphological similarities as perceived by those early workers, and those groups were then grouped according to
their similarities, and so on, to form a hierarchy"
[3] [Oxford English Dictionary, Third Edition, January 2009: Urochordata
[4] http:/ / toolserver. org/ ~verisimilus/ Timeline/ Timeline. php?Ma=555
[5] http:/ / toolserver. org/ ~verisimilus/ Timeline/ Timeline. php?Ma=558
[6] http:/ / toolserver. org/ ~verisimilus/ Timeline/ Timeline. php?Ma=541
[7] http:/ / toolserver. org/ ~verisimilus/ Timeline/ Timeline. php?Ma=549–543
[8] Ernettia is from the Kuibis formation, approximate date given by
[9] http:/ / toolserver. org/ ~verisimilus/ Timeline/ Timeline. php?Ma=518
[10] http:/ / toolserver. org/ ~verisimilus/ Timeline/ Timeline. php?Ma=542
[11] http:/ / toolserver. org/ ~verisimilus/ Timeline/ Timeline. php?Ma=900
[12] http:/ / toolserver. org/ ~verisimilus/ Timeline/ Timeline. php?Ma=896
[13] Benton, M.J. (2004). Vertebrate Palaeontology, Third Edition. Blackwell Publishing, 472 pp. The classification scheme is available online
(http:/ / palaeo. gly. bris. ac. uk/ benton/ vertclass. html)
External links
•
•
•
•
Chordate (http://www.eol.org/pages/694) at the Encyclopedia of Life
Chordate on GlobalTwitcher.com (http://www.globaltwitcher.com/taxa_class.asp?phylaid=1)
Chordate node at Tree Of Life (http://tolweb.org/Chordata/2499)
Chordate node at NCBI Taxonomy (http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.
cgi?id=7711)
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Article Sources and Contributors
Article Sources and Contributors
Chordate Source: http://en.wikipedia.org/w/index.php?oldid=576089267 Contributors: 07joe2k7, 4444hhhh, 61x62x61, A-giau, A. Parrot, ACW, Abigail-II, Abrech, AiaiaiPUFFS,
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Kaninchen, Jauhienij, Jimfbleak, JoJan, Joedaguy, Joelmills, Joelr31, JoergenB, JohnOwens, Johnrob69, JonRichfield, JorisvS, Josh Grosse, Jredytjsfd, Justin, Katya0133, Kbh3rd, Keenan
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Macrakis, Mad Greg, ManfromButtonwillow, Mani1, Mark t young, Marysunshine, Materialscientist, Matijap, Mav, Maximus Rex, Mditto, Medeis, Megalobingosaurus, Mentifisto, MichaK,
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Image Sources, Licenses and Contributors
file:Pristella maxillaris.jpg Source: http://en.wikipedia.org/w/index.php?title=File:Pristella_maxillaris.jpg License: Creative Commons Attribution-Sharealike 2.5 Contributors: Richard Bartz,
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Image:Pacific hagfish Myxine.jpg Source: http://en.wikipedia.org/w/index.php?title=File:Pacific_hagfish_Myxine.jpg License: Public Domain Contributors: EugeneZelenko, Infrogmation,
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Image:Branchiostoma lanceolatum.jpg Source: http://en.wikipedia.org/w/index.php?title=File:Branchiostoma_lanceolatum.jpg License: unknown Contributors: Amada44, Berrucomons,
Biopics, EnekoGotzon, Lycaon, Mmxx, NeverDoING, Nevit, Sanomi, 3 anonymous edits
Image:Eichelwurm.jpg Source: http://en.wikipedia.org/w/index.php?title=File:Eichelwurm.jpg License: GNU Free Documentation License Contributors: User Necrophorus on de.wikipedia
Image:Sandstar 300.jpg Source: http://en.wikipedia.org/w/index.php?title=File:Sandstar_300.jpg License: Public Domain Contributors: Eugene van der Pijll, Haplochromis, JoJan, Liné1,
Lucero del Alba, Lycaon, Xhienne
Image:Haikouichthys4.png Source: http://en.wikipedia.org/w/index.php?title=File:Haikouichthys4.png License: Public Domain Contributors: User:Giant Blue Anteater
Image:BlueWhaleSkeleton.jpg Source: http://en.wikipedia.org/w/index.php?title=File:BlueWhaleSkeleton.jpg License: GNU Free Documentation License Contributors: Bronwen Lea
File:Peregrine Falcon 12.jpg Source: http://en.wikipedia.org/w/index.php?title=File:Peregrine_Falcon_12.jpg License: Creative Commons Attribution-Sharealike 3.0 Contributors: Ltshears
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