Teleostomi is an obsolete
clade of
jawed vertebrates that supposedly includes the
tetrapod
Tetrapods (; ) are four-limbed vertebrate animals constituting the superclass Tetrapoda (). It includes extant and extinct amphibians, sauropsids (reptiles, including dinosaurs and therefore birds) and synapsids (pelycosaurs, extinct therapsid ...
s,
bony fish
Osteichthyes (), popularly referred to as the bony fish, is a diverse superclass of fish that have skeletons primarily composed of bone tissue. They can be contrasted with the Chondrichthyes, which have skeletons primarily composed of cartilag ...
, and the wholly extinct
acanthodian
Acanthodii or acanthodians is an extinct class of gnathostomes (jawed fishes), typically considered a paraphyletic group. They are currently considered to represent a grade of various fish lineages leading up to the extant Chondrichthyes, which ...
fish. Key characters of this group include an
operculum and a single pair of respiratory openings, features which were lost or modified in some later representatives. The teleostomes include all jawed vertebrates except the
chondrichthyans
Chondrichthyes (; ) is a class that contains the cartilaginous fishes that have skeletons primarily composed of cartilage. They can be contrasted with the Osteichthyes or ''bony fishes'', which have skeletons primarily composed of bone tissue. ...
and the
extinct class
Class or The Class may refer to:
Common uses not otherwise categorized
* Class (biology), a taxonomic rank
* Class (knowledge representation), a collection of individuals or objects
* Class (philosophy), an analytical concept used differently ...
Placodermi.
Recent studies indicate that
Osteichthyes evolved from
placoderms like ''
Entelognathus
''Entelognathus primordialis'' (“primordial complete jaw”) is a maxillate placoderm from the late Silurian (Ludlow epoch) of Qujing, Yunnan, 419 million years ago.
A team led by Min Zhu of the Academy of Sciences' Institute of Vertebrate Pa ...
'', while acanthodians are more closely related to modern chondrichthyes. Teleostomi, therefore, is not a valid, natural clade, but a
polyphyletic group of species.
The clade Teleostomi should not be confused with the similar-sounding fish clade
Teleostei
Teleostei (; Greek ''teleios'' "complete" + ''osteon'' "bone"), members of which are known as teleosts ), is, by far, the largest infraclass in the class Actinopterygii, the ray-finned fishes, containing 96% of all extant species of fish. Tele ...
.
Origins
The origins of the teleostomes are obscure. They are traditionally assumed to be descendants of the
Acanthodian
Acanthodii or acanthodians is an extinct class of gnathostomes (jawed fishes), typically considered a paraphyletic group. They are currently considered to represent a grade of various fish lineages leading up to the extant Chondrichthyes, which ...
s ("spiny sharks") from the
Early Silurian Period; however, more recent discoveries show that the "spiny sharks" are actually a paraphyletic assemblage leading to
Chondrichthyes
Chondrichthyes (; ) is a class that contains the cartilaginous fishes that have skeletons primarily composed of cartilage. They can be contrasted with the Osteichthyes or ''bony fishes'', which have skeletons primarily composed of bone tissue. ...
, and that placoderms like ''
Entelognathus
''Entelognathus primordialis'' (“primordial complete jaw”) is a maxillate placoderm from the late Silurian (Ludlow epoch) of Qujing, Yunnan, 419 million years ago.
A team led by Min Zhu of the Academy of Sciences' Institute of Vertebrate Pa ...
'' are more closely related to true bony fish.
Living teleostomes constitute the clade
Euteleostomi
Euteleostomi (''Eu-teleostomi'', where ''Eu-'' comes from Greek εὖ 'well, good' or Euteleostomes, also known as "bony vertebrates") is a successful clade that includes more than 90% of the living species of vertebrates. Both its major subgro ...
, which includes all osteichthyans and tetrapods. Even after the acanthodians perished at the end of the
Permian, their euteleostome relatives flourished such that today they comprise 99% of living vertebrate species.
Physical characteristics
Teleostomes have two major adaptations that relate to
aquatic respiration. First, the early teleostomes probably had some type of
operculum; however, it was not the one-piece affair of living
fish. The development of a single respiratory opening seems to have been an important step. The second adaptation, the teleostomes also developed a primitive lung with the ability to use some atmospheric
oxygen. This developed, in later species, into the lung and (later) the swim bladder, used to keep the fish at neutral buoyancy.
Acanthodians share with Actinopterygii the characteristic of three
otoliths, the sagitta in the sacculus, the asteriscus in the lagena, and the lapillus in the utriculus. In dipnoans there are only two otoliths and in ''Latimeria'' there is only one.
However, most of the above synapomorphies can ultimately be found in several chondrichthyan groups.
Relationships
See also
*
Acanthodii
Acanthodii or acanthodians is an extinct class of gnathostomes (jawed fishes), typically considered a paraphyletic group. They are currently considered to represent a grade of various fish lineages leading up to the extant Chondrichthyes, which ...
*
Euteleostomi
Euteleostomi (''Eu-teleostomi'', where ''Eu-'' comes from Greek εὖ 'well, good' or Euteleostomes, also known as "bony vertebrates") is a successful clade that includes more than 90% of the living species of vertebrates. Both its major subgro ...
References
{{Taxonbar, from=Q134681
Vertebrate unranked clades
Late Ordovician first appearances
Extant Ordovician first appearances
Taxa named by Charles Lucien Bonaparte