# Surangular

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{{short description|Bone of the lower jaw}}
[[File:Proceratosaurus bradleyi Skull Reconstruction (alt).png|thumb|Skull diagram of the dinosaur ''[Proceratosaurus](/source/Proceratosaurus)'', showing location of surangular]]
[[File:Dimetrodon skull lateral.svg|thumb|Skull and jaws diagram of the primitive [synapsid](/source/Synapsida) ''[Dimetrodon](/source/Dimetrodon)'', showing location of surangular]]
The '''surangular'''{{efn|Alternately spelled supra-angular,<ref name="Gregory1917"/> supraangular,<ref name="Jollie1986"/><ref name="Schultze2008"/> suprangular, ''os supra-angulare'',<ref name="BaumelWitmer1993"/> or ''surangulare''.<ref name="BaumelWitmer1993"/>}} is a [jaw bone](/source/jaw_bone) found in most land [vertebrate](/source/vertebrate)s, except mammals. The surangular makes up the upper portion of the back half of the outside of the lower jaw, behind the [dentary](/source/dentary), above the [angular](/source/angular_bone), and outside the [articular](/source/articular). It is the main component of the outer wall of the adductor fossa, where the major jaw-closing muscles attach to the mandible.<ref name="Romer1956"/>

The surangular is ancestrally the posteriormost in the series of infradentary bones, which line the outside of the mandible below and behind the dentary bone.<ref name="Romer1956"/> It is also known as the '''fourth infradentary''' in early sarcopterygians, in which the infradentary series comprises four bones, the first being the [splenial](/source/splenial), the second the [postsplenial](/source/postsplenial), and third being the [angular](/source/angular_bone).<ref name="Porro2015"/>

In [archosaurs](/source/archosaurs) there is an opening, the external mandibular fenestra, found between the surangular, dentary, and angular.<ref name="Romer1956"/>

In some [eucynodonts](/source/eucynodonts), the surangular contacted the [squamosal](/source/squamosal_bone) to form part of the jaw joint, a characteristic that historically had been interpreted as a predecessor of the dentary-squamosal joint of mammals.<ref name="Rawson2024"/> The surangular was reduced to a tiny splint as part of the [evolution of mammalian auditory ossicles](/source/evolution_of_mammalian_auditory_ossicles) from other bones involved in the jaw joint, and absent in most mammals.<ref name="Han2017"/>

==Footnotes==
{{notelist}}

==References==
<references>
<ref name="BaumelWitmer1993">{{Cite book| pages = 46| last1 = Baumel| first1 = Julian J.| last2 = Witmer| first2 = Lawrence M.| title = Handbook of avian anatomy: nomina anatomica avium| chapter = Osteologia| location = Cambridge, Massachusetts| date = 1993}}</ref>
<ref name="Gregory1917">{{Cite journal| doi = 10.1130/GSAB-28-973| issn = 0016-7606| volume = 28| issue = 1| pages = 973–986| last = Gregory| first = William K.| title = Second report of the Committee on the Nomenclature of the Cranial Elements in the Permian Tetrapoda| journal = Bulletin of the Geological Society of America| date = 1917-01-01}}</ref>
<ref name="Han2017">{{Cite journal| doi = 10.1038/nature24483| issn = 0028-0836 | eissn = 1476-4687| volume = 551| issue = 7681| pages = 451–456| last1 = Han| first1 = Gang| last2 = Mao| first2 = Fangyuan| last3 = Bi| first3 = Shundong| last4 = Wang| first4 = Yuanqing| last5 = Meng| first5 = Jin| title = A Jurassic gliding euharamiyidan mammal with an ear of five auditory bones| journal = Nature| date = 2017-11-01}}</ref>
<ref name="Jollie1986">{{Cite journal| doi = 10.1139/z86-058| issn = 0008-4301 | volume = 64| issue = 2| pages = 365–379| last = Jollie| first = Malcolm| title = A primer of bone names for the understanding of the actinopterygian head and pectoral girdle skeletons| journal = Canadian Journal of Zoology| date = 1986-02-01}}</ref>
<ref name="Porro2015">{{Cite journal| doi = 10.1111/pala.12192| issn = 0031-0239 | eissn = 1475-4983| volume = 58| issue = 6| pages = 1031–1047| last1 = Porro| first1 = Laura B.| last2 = Rayfield| first2 = Emily J.| last3 = Clack| first3 = Jennifer A.| others = Zerina Johanson (ed.)| title = Computed tomography, anatomical description and three‐dimensional reconstruction of the lower jaw of Eusthenopteron foordi Whiteaves, 1881 from the Upper Devonian of Canada| journal = Palaeontology| date = 2015-08-21}}</ref>
<ref name="Rawson2024">{{Cite journal| publisher = Nature Publishing Group| doi = 10.1038/s41586-024-07971-3| issn = 1476-4687| volume = 634| issue = 8033| pages = 381–388| last1 = Rawson| first1 = James R. G.| last2 = Martinelli| first2 = Agustín G.| last3 = Gill| first3 = Pamela G.| last4 = Soares| first4 = Marina B.| last5 = Schultz| first5 = Cesar L.| last6 = Rayfield| first6 = Emily J.| title = Brazilian fossils reveal homoplasy in the oldest mammalian jaw joint| journal = Nature| date = 2024-09-25}}</ref>
<ref name=Romer1956>{{cite book | first1 = Alfred Sherwood | last1 = Romer | year = 1956 | title = The Osteology of the Reptiles | publisher = University of Chicago Press }}</ref>
<ref name="Schultze2008">{{Cite conference| publisher = Verlag Dr. Friedrich Pfeil| isbn = 978-3-89937-080-5| pages = 23–48| editor-first1 = Gloria | editor-last1 = Arratia | editor-first2 = Hans-Peter | editor-last2 = Schultze | editor-first3 = Mark V. H. | editor-last3 = Wilson | last = Schultze| first = Hans-Peter| title = Nomenclature and homologization of cranial bones in actinopterygians| book-title = Mesozoic fishes 4: Homology and phylogeny| location = München| date = 2008}}</ref>
</references>

{{Tetrapod osteology|S.}}

Category:Skull bones

{{Vertebrate anatomy-stub}}

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Adapted from the Wikipedia article [Surangular](https://en.wikipedia.org/wiki/Surangular) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Surangular?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.