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This shearing action is unique amongst living amniotes but has been compared with the chewing power stroke of mammals. We investigated details of the jaw movement using multibody dynamics analysis of an anatomically accurate three\u2010dimensional computer model constructed from computed tomography scans. The model predicts that a flexible symphysis is necessary for changes in the intermandibular angle that permits prooral movement. Models with the greatest symphysial flexibility allow the articulation surface of the articular to follow the quadrate cotyle with the least restriction, and suggest that shearing is accompanied by a long axis rotation of the lower jaws. This promotes precise point loading between the cutting edges of particular teeth, enhancing the effectiveness of the shearing action. Given that <jats:italic>Sphenodon<\/jats:italic> is a relatively inactive reptile, we suggest that the link between oral food processing and endothermy has been overstated. Food processing improves feeding efficiency, a consideration of particular importance when food availability is unpredictable. Although this feeding mechanism is today limited to <jats:italic>Sphenodon<\/jats:italic>, a survey of fossil rhynchocephalians suggests that it was once more widespread. Anat Rec, 2012. \u00a9 2012 Wiley\u2010Periodicals, Inc.<\/jats:p>","DOI":"10.1002\/ar.22487","type":"journal-article","created":{"date-parts":[[2012,5,30]],"date-time":"2012-05-30T01:09:09Z","timestamp":1338340149000},"page":"1075-1091","source":"Crossref","is-referenced-by-count":44,"title":["Shearing Mechanics and the Influence of a Flexible Symphysis During Oral Food Processing in <i>Sphenodon<\/i> (Lepidosauria: Rhynchocephalia)"],"prefix":"10.1002","volume":"295","author":[{"given":"Marc E.H.","family":"Jones","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Paul","family":"O'higgins","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Michael J.","family":"Fagan","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Susan E.","family":"Evans","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Neil","family":"Curtis","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"311","published-online":{"date-parts":[[2012,5,30]]},"reference":[{"key":"e_1_2_8_2_1","doi-asserted-by":"publisher","DOI":"10.1017\/S0094837300013956"},{"key":"e_1_2_8_3_1","doi-asserted-by":"publisher","DOI":"10.1038\/nature01995"},{"key":"e_1_2_8_4_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.cretres.2011.10.014"},{"key":"e_1_2_8_5_1","doi-asserted-by":"publisher","DOI":"10.1242\/jeb.033712"},{"key":"e_1_2_8_6_1","doi-asserted-by":"publisher","DOI":"10.1242\/jeb.020586"},{"key":"e_1_2_8_7_1","doi-asserted-by":"publisher","DOI":"10.1017\/CBO9780511549717.004"},{"key":"e_1_2_8_8_1","first-page":"91","article-title":"The evolution of feeding mechanisms in early sauropodomorph dinosaurs","volume":"77","author":"Barrett PM","year":"2007","journal-title":"Sp Pap Palaeontol"},{"key":"e_1_2_8_9_1","volume-title":"The development of the vertebrate skull","author":"de Beer","year":"1937"},{"key":"e_1_2_8_10_1","doi-asserted-by":"publisher","DOI":"10.1039\/9781847552143"},{"key":"e_1_2_8_11_1","doi-asserted-by":"publisher","DOI":"10.1111\/j.1469-1795.2010.00386.x"},{"key":"e_1_2_8_12_1","doi-asserted-by":"publisher","DOI":"10.1086\/physzool.63.4.30158172"},{"key":"e_1_2_8_13_1","doi-asserted-by":"publisher","DOI":"10.1111\/j.1096-3642.1946.tb00117.x"},{"key":"e_1_2_8_14_1","first-page":"1","article-title":"A pleurosaur from the lower Jurassic and the taxonomic position of the Sphenodontida","volume":"189","author":"Carroll RL","year":"1985","journal-title":"Palaeontol Abt A"},{"key":"e_1_2_8_15_1","first-page":"70","volume-title":"the shadow of the dinosaurs: early Mesozoic tetrapods","author":"Carroll RC","year":"1994"},{"key":"e_1_2_8_16_1","doi-asserted-by":"publisher","DOI":"10.1007\/s003600050179"},{"key":"e_1_2_8_17_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.geobios.2010.04.001"},{"key":"e_1_2_8_18_1","unstructured":"CITES.2011Appendices I II and III. 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