The postdentary trough is a skeletal feature seen in
Mesozoic mammals. It is found on the inside of the lower jaw (
dentary
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 ...
), at the back behind the molar teeth. It is the hollow in which the postdentary bones and
Meckel's cartilage
In humans, the cartilaginous bar of the mandibular arch is formed by what are known as Meckel's cartilages (right and left) also known as Meckelian cartilages; above this the incus and malleus are developed. Meckel's cartilage arises from the firs ...
sit. These bones form the middle ear in later mammal groups (see
Evolution of mammalian auditory ossicles
The evolution of mammalian auditory ossicles was an evolutionary event that resulted in the formation of the bones of the mammalian middle ear. These bones, or ossicles, are a defining characteristic of all mammals. The event is well-documented an ...
); they include the
incus
The ''incus'' (plural incudes) or anvil is a bone in the middle ear. The anvil-shaped small bone is one of three ossicles in the middle ear. The ''incus'' receives vibrations from the ''malleus'', to which it is connected laterally, and transm ...
(
quadrate),
malleus
The malleus, or hammer, is a hammer-shaped small bone or ossicle of the middle ear. It 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 fr ...
(
articular
The articular bone is part of the lower jaw of most vertebrates, including most jawed fish, amphibians, birds and various kinds of reptiles, as well as ancestral mammals.
Anatomy
In most vertebrates, the articular bone is connected to two oth ...
), ectotympanic (
angular) and prearticular.
[Zhe-Xi Luo 201]
Developmental patterns in Mesozoic evolution of mammal ears
Annual Review of Ecology, Evolution, and Systematics, 42, 355-380
In
Mesozoic mammals these bones gradually change position and size until they are incorporated in the middle ear.
References
Mammal anatomy
Evolution of mammals
{{Vertebrate anatomy-stub