Editing Skull (section)

===Tetrapods===
The skulls of the earliest [[tetrapod]]s closely resembled those of their [[ancestor]]s amongst the [[lobe-finned fish]]es. The [[skull roof]] is formed of a series of plate-like bones, including the maxilla, [[frontal bone|frontals]], [[parietal bone|parietal]]s, and [[lacrimal bone|lacrimal]]s, among others. It is overlaying the [[endocranium]], corresponding to the cartilaginous skull in sharks and [[Batoidea|rays]]. The various separate bones that compose the temporal bone of humans are also part of the skull roof series. A further plate composed of four pairs of bones forms the roof of the mouth; these include the [[vomer]] and [[palatine bone]]s. The base of the cranium is formed from a ring of bones surrounding the foramen magnum and a median bone lying further forward; these are [[homology (biology)|homologous]] with the occipital bone and parts of the sphenoid in mammals. Finally, the lower jaw is composed of multiple bones, only the most anterior of which (the dentary) is homologous with the mammalian mandible.<ref name="VB">{{cite book |last1=Romer |first1=Alfred Sherwood |last2=Parsons |first2=Thomas S. |year=1977 |title=The Vertebrate Body |publisher=Holt-Saunders International |location= Philadelphia, PA |pages=216–247 |isbn=0-03-910284-X}}</ref>

In living tetrapods, a great many of the original bones have either disappeared or fused into one another in various arrangements.

====Birds====
[[File:CuckooSkull.jpg|thumb|Cuckoo skull]]

[[Bird]]s have a [[diapsid]] skull, as in reptiles, with a prelacrimal fossa (present in some reptiles). The skull has a single occipital condyle.<ref>{{Cite book|url=https://archive.org/details/naturalhistoryof033252mbp|title=Natural History of Birds|last=Wing|first=Leonard W.|publisher=The Ronald Press Company|year=1956|pages=[https://archive.org/details/naturalhistoryof033252mbp/page/n25 22]–23|chapter=The Place of Birds in Nature}}</ref> The skull consists of five major bones: the frontal (top of head), parietal (back of head), premaxillary and nasal (top beak), and the mandible (bottom beak). The skull of a normal bird usually weighs about 1% of the bird's total bodyweight. The eye occupies a considerable amount of the skull and is surrounded by a sclerotic eye-ring, a ring of tiny bones. This characteristic is also seen in reptiles.

====Amphibians====
[[File:AmphibSkeletons.png|thumb|upright=.8|Amphibians' skulls, Hans Gadow, 1909 ''Amphibia and Reptiles'']]

Living [[amphibian]]s typically have greatly reduced skulls, with many of the bones either absent or wholly or partly replaced by cartilage.<ref name="VB" /> In mammals and birds, in particular, modifications of the skull occurred to allow for the expansion of the brain. The fusion between the various bones is especially notable in birds, in which the individual structures may be difficult to identify.