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The quadrate bone is a skull bone in most tetrapods, including amphibians, sauropsids (reptiles, birds), and early synapsids. 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 ...
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. [5]
Their quadrate bone articulation with the lower jaw resembled that of a pelican or other birds that can open their beak widely. Altogether, the pseudotooth birds would have filled an ecological niche almost identical to that of the larger fish-eating pteranodontian pterosaurs , whose extinction at the end of the Cretaceous may well have paved ...
Mounted skull of a python with disarticulated upper and lower jaw joints. In snakes, the columella would be attached directly to the quadrate bone (c). Snakes have lost a tympanic membrane, and hence a distal attachment for the columella. The columella is instead connected to the quadrate bone of the jaw. Thus, snakes are able to detect and ...
The prefrontal is a smaller bone on the side margin of the skull roof between the frontal, lacrimal, and nasal. [25]: 38 predentary The predentary is an unpaired bone found in front of the dentaries of the lower jaw that formed the lower beak in ornithischians. [1]: 142 Its presence is considered an ornithischian synapomorphy. [99] premaxilla
Streptostyly is the fore-aft movement of the quadrate about the otic joint (quadratosquamosal joint), although transverse movements may also be possible. [2] Many hypothesized types of kinesis require basal joint kinesis ( neurokinesis of Iordansky, 1990), that is, movement between the braincase and palate at the basipterygoid joint.
The bone forms an ancestral component of the dermal roof and is typically thin compared to other skull bones. [3] The squamosal bone lies ventral to the temporal series and otic notch, and is bordered anteriorly by the postorbital. Posteriorly, the squamosal articulates with the quadrate and pterygoid bones.
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 ...