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In most tetrapods, the quadrate bone connects to the quadratojugal and squamosal bones in the skull, and forms upper part of the jaw joint. The lower jaw articulates at the articular bone, located at the rear end of the lower jaw. The quadrate bone forms the lower jaw articulation in all classes except mammals. [1]
In mammals, the quadrate bone evolves to form the incus, one of the ossicles of the mammalian ear. [5] Similarly, the articular bone evolves to form the malleus. The squamosal bone migrates and lengthens to become a new point of articulation with the lower jaw (at the dentary bone). [3]
In the mammal configuration, the quadrate and articular bones are much smaller and form part of the middle ear. Note that in mammals the lower jaw consists of only the dentary bone. 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 ...
In other words, jaw joints and ears do not define any except the most recent groups of mammals. Mammalian and non-mammalian jaws. In the mammal configuration, the quadrate and articular bones are much smaller and form part of the middle ear. Note that in mammals the lower jaw consists of only the dentary bone. [24]
In mammals, the jaws are made up of the mandible (lower jaw) and the maxilla (upper jaw). In the ape , there is a reinforcement to the lower jaw bone called the simian shelf . In the evolution of the mammalian jaw, two of the bones of the jaw structure (the articular bone of the lower jaw, and quadrate ) were reduced in size and incorporated ...
In mammals, most have disappeared, leaving only the mandible. As a result, there is only articulation between the mandible and temporal bones, as opposed to articulation between articular and quadrate bones. An intermediate stage can be seen in some therapsids, in which both points of articulation are
The condyloid process or condylar process is the process on the human and other mammalian species' mandibles that ends in a condyle, the mandibular condyle.It is thicker than the coronoid process of the mandible and consists of two portions: the condyle and the constricted portion which supports it, the neck.
In tetrapods with a quadratojugal bone, it often forms a portion of the jaw joint. Developmentally, the quadratojugal bone is a dermal bone in the temporal series, forming the original braincase . The squamosal and quadratojugal bones together form the cheek region [ 4 ] and may provide muscular attachments for facial muscles.