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The articular bone is part of the lower jaw of most
vertebrates Vertebrates () comprise all species of animals within the subphylum Vertebrata () (chordates with backbones). Vertebrates represent the overwhelming majority of the phylum Chordata, with currently about 69,963 species described. Vertebrates inclu ...

vertebrates
, including most
jawed fish Gnathostomata are the jawed vertebrates. The term derives from Greek: (') "jaw" + (') "mouth". Gnathostome diversity comprises roughly 60,000 species, which accounts for 99% of all living vertebrates. In addition to opposing jaws, living gnath ...

jawed fish
,
amphibians Amphibians are ectothermic, tetrapod vertebrates of the class Amphibia. All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terrestrial, fossorial, arboreal or fresh ...

amphibians
,
birds Birds are a group of warm-blooded vertebrates constituting the class Aves , characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweight skele ...

birds
and various kinds of
reptiles Reptiles are tetrapod animals in the class or clade Reptilia . As a class in Linnean taxonomy, Reptilia refers to a paraphyletic grouping comprising all amniotes (vertebrates which encase their embryos in a series of protective sacs) except syn ...

reptiles
, as well as ancestral
mammals Mammals (from Latin , 'breast') are a group of vertebrate animals constituting the class Mammalia (), and characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region ...

mammals
.


Anatomy

In most animals, the articular bone is connected to two other lower jaw bones, the
suprangular The suprangular or surangular is a jaw bone found in most land vertebrates, except mammals. Usually in the back of the jaw, on the upper edge, it is connected to all other jaw bones: dentary, angular, splenial and articular. It is often a muscle at ...

suprangular
and the
angular
angular
. Developmentally, it originates from the embryonic mandibular cartilage. The most
caudal Caudal may refer to: Anatomy * Caudal (anatomical term) (from Latin ''caudum''; tail), used to describe how close something is to the trailing end of an organism * Caudal artery, the portion of the dorsal aorta of a vertebrate that passes into the ...

caudal
portion of the mandibular cartilage ossifies to form the articular bone, while the remainder of the mandibular cartilage either remains cartilaginous or disappears.


In snakes

In
snakes Snakes are elongated, limbless, carnivorous reptiles of the suborder Serpentes . Like all other squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales. Many species of snakes have skulls with several more joints th ...

snakes
, the articular, surangular, and prearticular bones have fused to form the compound bone. The mandible is suspended from the quadrate bone and articulates at this compound bone.


Function


In amphibians and reptiles

In most tetrapods, the articular bone forms the lower portion of the jaw joint. The upper jaw articulates at the
quadrate bone 300px|A schematic of an anapsid skull showing the location of major dermal bones of the upper skull, including the quadrate bone (q).The quadrate bone is a skull bone in most tetrapods, including amphibians, sauropsids (reptiles, birds), and early ...

quadrate bone
.


In mammals

In
mammals Mammals (from Latin , 'breast') are a group of vertebrate animals constituting the class Mammalia (), and characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region ...

mammals
, the articular bone evolves to form the
malleus The malleus or hammer is a hammer-shaped small bone or ossicle of the middle ear which connects with the incus and is attached to the inner surface of the eardrum. The word is Latin for ''hammer'' or ''mallet''. It transmits the sound vibrations f ...

malleus
, one of the mammalian
ossicles The ossicles (also called auditory ossicles) are three bones in either middle ear that are among the smallest bones in the human body. They serve to transmit sounds from the air to the fluid-filled labyrinth (cochlea). The absence of the auditory ...

ossicles
of the middle ear. This is an
apomorphy 279px|trait states.">Phenotypic trait">trait states. In phylogenetics, apomorphy and synapomorphy refer to derived characters of a clade: characters or traits that are derived from ancestral characters over evolutionary history. An apomorphy is a c ...

apomorphy
of the mammalian clade, and is used to determine the fossil transition to mammals. It is
analogous Analogy (from Greek ἀναλογία, ''analogia'', "proportion", from ''ana-'' "upon, according to" lso "against", "anew"+ ''logos'' "ratio" lso "word, speech, reckoning" is a cognitive process of transferring information or meaning from a partic ...

analogous
to, but not to the
articular process The articular processes or zygapophyses (Greek ζυγον = "yoke" (because it links two vertebrae) + απο = "away" + φυσις = "process") of a vertebra are projections of the vertebra that serve the purpose of fitting with an adjacent vertebra ...

articular process
of the
lower jaw In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath the maxilla. It is the only movable bone of ...

lower jaw
. After the loss of the quadrate-articular joint, the squamosal and dentary bones form the new jaw joint in mammals.


References

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