| Chordates Fossil range: Cambrian – Recent |
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 Yellowfin tuna, Thunnus albacares
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Chordates (phylum Chordata) are a group of animals that includes the vertebrates, together with several closely related invertebrates. The Cambrian is a geologic period and system that began about Ma (million years ago at the end of the Proterozoic eon and ended about Ma with The yellowfin tuna ( Thunnus albacares) is a type of Tuna. It is found in open waters of Tropical and subtropical Seas worldwide Animals Plants fungi, and Protists are eukaryotes (juːˈkærɪɒt or -oʊt Organisms whose cells are organized into complex Eumetazoa is a Clade comprising all major Animal groups except sponges Characteristics of eumetazoans include true tissues organized into The Bilateria (ˌbaɪləˈtɪəriə are all animals having a bilateral symmetry, i Deuterostomes (taxonomic term Deuterostomia; from the Greek "second mouth" are a superphylum of Animals They are a subtaxon of the William Bateson ( Robin Hood's Bay, August 8 1861 &ndash February 8 1926 was a British Geneticist, a Fellow of St Year 1885 ( MDCCCLXXXV) was a Common year starting on Thursday (link will display the full calendar of the Gregorian calendar (or a Common A class is the Taxonomic rank in the Biological classification of organisms in Biology below phylum and above order. Chordates ( Phylum Chordata) are a group of Animals that includes the Vertebrates together with several closely related Invertebrates A phylum ( Plural: phyla) is a Taxonomic rank between Kingdom and above Class. Vertebrates are members of the Subphylum Vertebrata, Chordates with backbones or spinal columns The grouping sometimes includes An invertebrate is an Animal lacking a Vertebral column. The group includes 98% of all animal Species — all animals except those in the Chordate They are united by having, at some time in their life cycle, a notochord, a hollow dorsal nerve cord, pharyngeal slits, an endostyle, and a post-anal tail. The notochord is a flexible rod-shaped body found in Embryos of all Chordates It is composed of cells derived from the Mesoderm and defines the The dorsal nerve cord is one of the embryonic features unique to Chordates along with a Notochord, a post-anal tail and Pharyngeal slits The dorsal nerve Pharyngeal slits, characteristic of both Hemichordata and Chordata, are used by organisms in Feeding. An endostyle is a longitudinal Ciliated groove on the Ventral wall of the Pharynx which produces Mucus to gather food particles The tail is the section at the rear end of an Animal 's Body; in general the term refers to a distinct flexible Appendage to the Torso. Some scientists argue that the true qualifier should be pharyngeal pouches rather than slits. In the development of vertebrate animals, Pharyngeal or branchial pouches form on the endodermal side between the Branchial arches and pharyngeal
The phylum Chordata is broken down into three subphyla: Urochordata, Cephalochordata, and Vertebrata. Tunicate, also known as urochordata, tunicata (and by the common names of urochordates, sea squirts, and sea pork) is the The lancelets (subphylum Cephalochordata, traditionally known as amphioxus) are a group of primitive Chordates. Vertebrates are members of the Subphylum Vertebrata, Chordates with backbones or spinal columns The grouping sometimes includes Some consider the Hemichordata a fourth chordate subphylum, but they are usually treated as a separate phylum. Hemichordata is a phylum of worm-shaped marine Deuterostome Animals generally considered the sister group of the Echinoderms They date Urochordate larvae have a notochord and a nerve cord but these are lost in adulthood. Cephalochordates have a notochord and a nerve cord but no vertebrae. A vertebra (plural vertebrae) is an individual Irregular bone in the spinal or Vertebral column ( aka ischis a flexuous and flexible column In all vertebrates except for Hagfish, the dorsal hollow nerve cord has been surrounded with cartilaginous or bony vertebrae and the notochord generally reduced. Hagfish are marine Craniates of the class Myxini, also known as Hyperotreti. Cartilage is a type of dense Connective tissue. It is composed of specialized cells called chondrocytes that produce a large amount of extracellular matrix
The chordates and three sister phyla, the hemichordates, the echinoderms and the xenoturbellidae, make up the deuterostomes, a superphylum. A phylum ( Plural: phyla) is a Taxonomic rank between Kingdom and above Class. Hemichordata is a phylum of worm-shaped marine Deuterostome Animals generally considered the sister group of the Echinoderms They date Echinoderms (Phylum Echinodermata) are a phylum of marine Animals (including Sea stars) Xenoturbella is a Genus of Bilaterian animals it contains two marine Worm -like species Deuterostomes (taxonomic term Deuterostomia; from the Greek "second mouth" are a superphylum of Animals They are a subtaxon of the A phylum ( Plural: phyla) is a Taxonomic rank between Kingdom and above Class. The chordates are the largest phylum among the deuterostomes.
The extant groups of chordates are related as shown in the phylogenetic tree below. A phylogenetic tree, also called an evolutionary tree, is a tree showing the Evolutionary relationships among various biological Species or other Many of the taxa listed do not match traditional classes because several of those classes are paraphyletic. In Phylogenetics, a group of organisms is said to be paraphyletic if the group contains its most recent common ancestor but does not contain all Different attempts to organize the profusion of chordate clades into a small number of groups, some with and some without paraphyletic taxa, have thrown vertebrate classification into a state of flux. A clade is a taxonomic group comprising a single Common ancestor and all the descendants of that ancestor Also, the relationships of some chordate groups are not very well understood.
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Classification
Taxonomy
The following schema is from the third edition of Vertebrate Palaeontology. Taxonomy is the practice and science of classification The word comes from the Greek, taxis (meaning 'order' 'arrangement' and, nomos Vertebrate Palaeontology is a basic textbook on Vertebrate paleontology by Michael J [1] While it is structured so as to reflect evolutionary relationships (similar to a cladogram), it also retains the traditional ranks used in Linnaean taxonomy. Cladistics is the hierarchical classification of Species based on evolutionary ancestry Linnaean taxonomy is a method of classifying living things originally devised by (and named for Carolus Linnaeus, although it has changed considerably since his time
- Phylum Chordata
- Subphylum Tunicata (Urochordata)— (tunicates, 3,000 species)
- Subphylum Cephalochordata (Acraniata)— (lancelets, 30 species)
- Subphylum Vertebrata (Craniata) (vertebrates — animals with backbones; 57,674 species)
- Class 'Agnatha'* (jawless vertebrates; 100+ species)
- Subclass Myxinoidea (hagfish; 65 species)
- Subclass Petromyzontida (Lampreys)
- Subclass Conodonta
- Subclass Pteraspidomorphi (Paleozoic jawless fish)
- Order Anaspida
- Order Thelodonti (Paleozoic jawless fish)
- Infraphylum Gnathostomata (jawed vertebrates)
- Class Placodermi (Paleozoic armoured forms)
- Class Chondrichthyes (cartilaginous fish; 900+ species)
- Class Acanthodii (Paleozoic "spiny sharks")
- Class Osteichthyes (bony fishes; 30,000+ species)
- Subclass Actinopterygii (ray-finned fish; about 30,000 species)
- Subclass Sarcopterygii (lobe-finned fish)
- Superclass Tetrapoda (four-legged vertebrates; 18,000+ species)
- Class 'Agnatha'* (jawless vertebrates; 100+ species)
Phylogeny
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Note: Lines show probable evolutionary relationships, including extinct taxa, which are denoted with a dagger, †. Tunicate, also known as urochordata, tunicata (and by the common names of urochordates, sea squirts, and sea pork) is the The lancelets (subphylum Cephalochordata, traditionally known as amphioxus) are a group of primitive Chordates. Vertebrates are members of the Subphylum Vertebrata, Chordates with backbones or spinal columns The grouping sometimes includes For the class of Brachiopods see Craniforma. Craniata (sometimes Craniota) is a proposed Clade of Agnatha ( Greek, "no jaws" is a Paraphyletic superclass of jawless fish in the phylum Chordata, subphylum Vertebrata In Phylogenetics, a group of organisms is said to be paraphyletic if the group contains its most recent common ancestor but does not contain all Hagfish are marine Craniates of the class Myxini, also known as Hyperotreti. A lamprey (sometimes also called lamprey eel) is a Jawless fish with a toothed funnel-like sucking mouth Conodonts are extinct chordates resembling eels classified in the class Conodonta. Pteraspidomorphi is an extinct subclass of early Jawless fish. For turtles see Anapsida. The Anaspida ("Without Shields" are stem Gnathostomes, and are classically regarded as There is much debate over whether the clade of Palaeozoic fish known as the Thelodonti (formerly coelolepids) represent a monophyletic grouping, or disparate Gnathostomata is the group of Vertebrates with Jaws The group is traditionally a superclass, including the familiar classes of Fish, The jaw is either of the two opposable structures forming or near the entrance to the Mouth. The Placodermi were a class of armoured Prehistoric fishes known from Fossils which lived from the late Silurian to the end of the Devonian Chondrichthyes or cartilaginous fishes are jawed Fish with paired fins paired nostrils scales two-chambered hearts and skeletons made of Cartilage rather Acanthodii (sometimes called spiny sharks) is a class of extinct Fishes having features of both bony fish ( Osteichthyes) and cartilaginous fish ( Osteichthyes (ˌɒstiːˈɪkθiːz also called bony fish, are a taxonomic Class of Fish that includes the ray-finned fish ( Actinopterygii The Actinopterygii (the plural form of Actinopterygius) comprise the class of the ray-finned fishes. Sarcopterygii (from Greek σαρξ sarx, flesh and πτερυξ pteryx, fin is traditionally the class of lobe-finned Fishes consisting Tetrapods ( Greek τετραποδη tetrapoda, Latin Quadruped, "four-footed" are Vertebrate Animals Prehistoric amphibian Amphibians (class Amphibia such as Frogs Toads Salamanders Newts Gymnophiona, Sirens and The amniotes are a group of Tetrapod Vertebrates that include the Synapsida ( Mammals and Mammal-like reptiles and Sauropsida Reptiles, or members of the class Reptilia are air-breathing Cold-blooded Vertebrates that have skin covered in scales as opposed to hair or feathers Birds ( class Aves) are bipedal endothermic ( Warm-blooded) Vertebrate animals that lay eggs. Synapsids ('fused arch' also known as theropsids ('beast face' are a class of Animals that includes Mammals and everything closer to mammals than Mammals ( class Mammalia) are a class of Vertebrate Animals characterized by the presence of Sweat glands, including sweat glands Tunicate, also known as urochordata, tunicata (and by the common names of urochordates, sea squirts, and sea pork) is the The Appendicularia, Larvaceans or KiK are a group of solitary free-swimming pelagic Urochordates found throughout The Appendicularia, Larvaceans or KiK are a group of solitary free-swimming pelagic Urochordates found throughout The Thalicea comprise a class of marine animals within the subphylum Urochordata. Ascidiacea (commonly known as the ascidians or Sea squirts is a class in the Tunicata Subphylum of sac-like marine Filter feeders The lancelets (subphylum Cephalochordata, traditionally known as amphioxus) are a group of primitive Chordates. For the class of Brachiopods see Craniforma. Craniata (sometimes Craniota) is a proposed Clade of Hagfish are marine Craniates of the class Myxini, also known as Hyperotreti. Vertebrates are members of the Subphylum Vertebrata, Chordates with backbones or spinal columns The grouping sometimes includes Conodonts are extinct chordates resembling eels classified in the class Conodonta. Cephalaspidomorphs are a Taxon of jawless fishes named for the cephalaspids a group of osteostracans. Hyperoartia is a group of Jawless fishes that includes the modern Lampreys and their Fossil relatives the jawless fishes of the class Pteraspidomorphi is an extinct subclass of early Jawless fish. Gnathostomata is the group of Vertebrates with Jaws The group is traditionally a superclass, including the familiar classes of Fish, The Placodermi were a class of armoured Prehistoric fishes known from Fossils which lived from the late Silurian to the end of the Devonian Chondrichthyes or cartilaginous fishes are jawed Fish with paired fins paired nostrils scales two-chambered hearts and skeletons made of Cartilage rather Teleostomi is a Clade of jawed vertebrates that includes the Tetrapods bony fish, and the wholly extinct acanthodian fish Acanthodii (sometimes called spiny sharks) is a class of extinct Fishes having features of both bony fish ( Osteichthyes) and cartilaginous fish ( Osteichthyes (ˌɒstiːˈɪkθiːz also called bony fish, are a taxonomic Class of Fish that includes the ray-finned fish ( Actinopterygii The Actinopterygii (the plural form of Actinopterygius) comprise the class of the ray-finned fishes. Sarcopterygii (from Greek σαρξ sarx, flesh and πτερυξ pteryx, fin is traditionally the class of lobe-finned Fishes consisting Tetrapods ( Greek τετραποδη tetrapoda, Latin Quadruped, "four-footed" are Vertebrate Animals Prehistoric amphibian Amphibians (class Amphibia such as Frogs Toads Salamanders Newts Gymnophiona, Sirens and The amniotes are a group of Tetrapod Vertebrates that include the Synapsida ( Mammals and Mammal-like reptiles and Sauropsida Synapsids ('fused arch' also known as theropsids ('beast face' are a class of Animals that includes Mammals and everything closer to mammals than Mammals ( class Mammalia) are a class of Vertebrate Animals characterized by the presence of Sweat glands, including sweat glands Reptiles, or members of the class Reptilia are air-breathing Cold-blooded Vertebrates that have skin covered in scales as opposed to hair or feathers Birds ( class Aves) are bipedal endothermic ( Warm-blooded) Vertebrate animals that lay eggs. A dagger ( †, &dagger U+ 2020 is a typographical symbol or Glyph. Some are invertebrates. Chordata is a phylum.
Origins
The origin of chordates is currently unknown. The first clearly-identifiable chordates are reduced fish- or lancelet-like specimens from the Cambrian. The lancelets (subphylum Cephalochordata, traditionally known as amphioxus) are a group of primitive Chordates. The Cambrian is a geologic period and system that began about Ma (million years ago at the end of the Proterozoic eon and ended about Ma with Most speculations about their origin fit into one or more of these categories:
- A sediment-dwelling worm-like animal that evolved a flatter body and/or fins for swimming.
- A sessile tubular filter-feeder that evolved into a free-swimming animal via usage of fins. (Tunicates, considered a chordate, are sessile filter feeders that have a tadpole-like larvae. Tunicate, also known as urochordata, tunicata (and by the common names of urochordates, sea squirts, and sea pork) is the )
- A drifting or swimming larva of some other kind of animal that eventually retained its swimming features into adulthood.
The notochord's stiffness in many chordates may have evolved to facilitate the effectiveness of alternating muscle contractions for swimming (in S-shaped movements). In other words, in order to bend the body, a muscle needs a rigid structure to pull against, and a notochord (at least before spines) is the main structure to provide this. Lack of a stiff body part would merely result in the shorting of the animal during muscle contractions instead of the bending motions needed for swimming.
External links
Dictionary
chordate
-noun
- A member of the phylum Chordata; numerous animals having a notochord at some stage of their development; in vertebrates this develops into the spine
-adjective
- Of such animals.
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