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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 vertebral column, backbones). Vertebrates represent the overwhelming majority of the phylum Chordata, with currently about 69,963 species described. ...
, including most
jawed fish Gnathostomata are the jawed vertebrate Vertebrates () comprise all species of animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological kingdom Animalia. With few excepti ...
,
amphibians Amphibians are ectothermic, tetrapod Tetrapods (; from Greek 'four' and 'foot') are four-limbed animals constituting the superclass Tetrapoda . It includes extant and extinct amphibians, reptiles (including dinosaurs and therefore bi ...
,
birds Birds are a group of warm-blooded vertebrate Vertebrates () comprise all species of animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological kingdom Animalia. With ...

birds
and various kinds of
reptiles Reptiles are tetrapod Tetrapods (; from Greek 'four' and 'foot') are four-limbed animals constituting the superclass Tetrapoda . It includes extant and extinct amphibians, reptiles (including dinosaurs and therefore birds), and synapsids ...

reptiles
, as well as ancestral
mammals Mammals (from Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the R ...
.


Anatomy

In most animals, the articular bone is connected to two other lower jaw bones, the suprangular and the angular. Developmentally, it originates from the embryonic mandibular cartilage. The most 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, carnivore, carnivorous reptiles of the suborder Serpentes . Like all other Squamata, squamates, snakes are ectothermic, amniote vertebrates covered in overlapping Scale (zoology), scales. Many species of snakes ...

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 ear ...
.


In mammals

In
mammals Mammals (from Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the R ...
, the articular bone evolves to form the
malleus The malleus or hammer is a hammer-shaped small bone or ossicle of the middle ear The middle ear is the portion of the ear internal to the eardrum, and external to the oval window of the inner ear. The mammalian middle ear contains three ossicl ...
, 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 (inner ear), labyrinth (cochlea). The a ...
of the middle ear. This is an
apomorphy 279px, trait states. In phylogenetics, apomorphy and synapomorphy refer to derived characters of a clade A clade (; from grc, , ''klados'', "branch"), also known as a monophyletic group or natural group, is a group of organisms that are mon ...
of the mammalian clade, and is used to determine the fossil transition to mammals. It is analogous to, but not homologous to the articular process of the . After the loss of the quadrate-articular joint, the squamosal and dentary bones form the new jaw joint in mammals.


References

Skeletal system Vertebrate anatomy {{Vertebrate-anatomy-stub