Quadrate bone: Difference between revisions
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{{Otheruses|Quadrate}} |
{{Otheruses|Quadrate}} |
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[[Image:Skull anapsida 1.svg|thumb|300px|[[Anapsid]] skull, Quadrate bone marked ''q'']] |
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The '''quadrate''' bone is part of a skull in most [[tetrapods]], including [[amphibians]], [[sauropsids]] ([[reptiles]], [[birds]]), and early [[synapsids]]. In these animals it connects to the [[quadratojugal]] and [[squamosal]] in the skull, and forms part of the jaw joint (the other part is the [[articular]] bone at the rear end of the lower jaw). |
The '''quadrate''' bone is part of a skull in most [[tetrapods]], including [[amphibians]], [[sauropsids]] ([[reptiles]], [[birds]]), and early [[synapsids]]. In these animals it connects to the [[quadratojugal]] and [[squamosal]] in the skull, and forms part of the jaw joint (the other part is the [[articular]] bone at the rear end of the lower jaw). |
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Revision as of 09:44, 5 January 2010
The quadrate bone is part of a skull in most tetrapods, including amphibians, sauropsids (reptiles, birds), and early synapsids. In these animals it connects to the quadratojugal and squamosal in the skull, and forms part of the jaw joint (the other part is the articular bone at the rear end of the lower jaw).
Evolutionary variation
In snakes, the quadrate bone has become elongated and very mobile, and contributes greatly to their ability to swallow very large prey items.
In mammals the articular and quadrate bones have migrated to the middle ear and are known as the malleus and incus. In fact, paleontologists regard this modification as the defining characteristic of mammalian hearing structures.[1] This migration was first described by Reichert in 1837. In pig embryos he discovered that the mandible ossifies on the side of Meckel's cartilage, while the posterior part of that cartilage is ossified and then detaches from the rest of the cartilage to enter the middle ear where it becomes the malleus. [2]
See also
Notes
- ^ "Mammaliformes: Overview". Palaeos. Retrieved January 2010.
{{cite web}}: Check date values in:|accessdate=(help) - ^ Scott 2000, Paragraph starting with "The original jaw bones changed also. [...] "
References
- Gilbert, Scott F. (c2000). "The anatomical tradition: Evolutionary Embryology: Embryonic homologies". Developmental Biology. Sunderland (MA): Sinauer Associates, Inc. (NCBI). Retrieved January 2010.
{{cite book}}: Check date values in:|accessdate=and|date=(help)
External links
- Image[dead link] - BioWeb at University of Wisconsin System
- "Dorsal View Snapping Turtle Skull (Photo)". Murray State University. Retrieved January 2010.
{{cite web}}: Check date values in:|accessdate=(help)
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