Surangular

{{short description|Bone of the lower jaw}} [[File:Proceratosaurus bradleyi Skull Reconstruction (alt).png|thumb|Skull diagram of the dinosaur ''Proceratosaurus'', showing location of surangular]] [[File:Dimetrodon skull lateral.svg|thumb|Skull and jaws diagram of the primitive synapsid ''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 found in most land vertebrates, except mammals. The surangular makes up the upper portion of the back half of the outside of the lower jaw, behind the dentary, above the angular, and outside the 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, the second the postsplenial, and third being the angular.<ref name="Porro2015"/>

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

In some eucynodonts, the surangular contacted the squamosal 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 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>

Category:Skull bones