{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,14]],"date-time":"2026-09-14T20:55:09Z","timestamp":1789419309039,"version":"build-2803163510"},"reference-count":75,"publisher":"Wiley","issue":"5","license":[{"start":{"date-parts":[[2013,9,16]],"date-time":"2013-09-16T00:00:00Z","timestamp":1379289600000},"content-version":"vor","delay-in-days":15,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"}],"funder":[{"name":"YPM's Divisions of Vertebrate Zoology and Vertebrate Paleontology, NSF Graduate Research Fellowship, NSF","award":["EF"],"award-info":[{"award-number":["EF"]}]},{"name":"YPM's Divisions of Vertebrate Zoology and Vertebrate Paleontology, NSF Graduate Research Fellowship, NSF","award":["0334966"],"award-info":[{"award-number":["0334966"]}]},{"name":"\u201cDeep Scaly: Assembling a Tree of Life for Squamata\u201d and the Yale Institute for Biospheric Studies"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Evolution and Development"],"published-print":{"date-parts":[[2013,9]]},"abstract":"<jats:title>SUMMARY<\/jats:title><jats:sec><jats:label\/><jats:p>The turtle shell represents a unique modification of the ancestral tetrapod body plan. The homologies of its approximately 50 bones have been the subject of debate for more than 200 years. Although most of those homologies are now firmly established, the evolutionary origin of the dorsal median nuchal bone of the carapace remains unresolved. We propose a novel hypothesis in which the nuchal is derived from the paired, laterally positioned cleithra\u2014dorsal elements of the ancestral tetrapod pectoral girdle that are otherwise retained among extant tetrapods only in frogs. This hypothesis is supported by origin of the nuchal as paired, mesenchymal condensations likely derived from the neural crest followed by a unique two\u2010stage pattern of ossification. Further support is drawn from the establishment of the nuchal as part of a highly conserved \u201cmuscle scaffold\u201d wherein the cleithrum (and its evolutionary derivatives) serves as the origin of the <jats:italic>Musculus trapezius<\/jats:italic>. Identification of the nuchal as fused cleithra is congruent with its general spatial relationships to other elements of the shoulder girdle in the adult morphology of extant turtles, and it is further supported by patterns of connectivity and transformations documented by critical fossils from the turtle stem group. The cleithral derivation of the nuchal implies an anatomical reorganization of the pectoral girdle in which the dermal portion of the girdle was transformed from a continuous lateral\u2010ventral arc into separate dorsal and ventral components. This transformation involved the reduction and eventual loss of the scapular rami of the clavicles along with the dorsal and superficial migration of the cleithra, which then fused with one another and became incorporated into the carapace.<\/jats:p><\/jats:sec>","DOI":"10.1111\/ede.12041","type":"journal-article","created":{"date-parts":[[2015,10,13]],"date-time":"2015-10-13T09:56:06Z","timestamp":1444730166000},"page":"317-325","source":"Crossref","is-referenced-by-count":50,"title":["Homology of the enigmatic nuchal bone reveals novel reorganization of the shoulder girdle in the evolution of the turtle shell"],"prefix":"10.1111","volume":"15","author":[{"given":"Tyler R.","family":"Lyson","sequence":"first","affiliation":[{"name":"Department of Geology and Geophysics Yale University New Haven CT 06511 USA"},{"name":"Division of Vertebrate Paleontology Yale Peabody Museum of Natural History New Haven CT 06511 USA"},{"name":"Department of Vertebrate Zoology National Museum of Natural History, Smithsonian Institution Washington DC 20560 USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Bhart\u2010Anjan S.","family":"Bhullar","sequence":"additional","affiliation":[{"name":"Department of Geology and Geophysics Yale University New Haven CT 06511 USA"},{"name":"Department of Organismic and Evolutionary Biology Harvard University Cambridge MA 02138 USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Gabe S.","family":"Bever","sequence":"additional","affiliation":[{"name":"Department of Geology and Geophysics Yale University New Haven CT 06511 USA"},{"name":"Department of Anatomy New York Institute of Technology, College of Osteopathic Medicine New York NY USA"},{"name":"Division of Paleontology American Museum of Natural History New York NY USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Walter G.","family":"Joyce","sequence":"additional","affiliation":[{"name":"Department of Geosciences University of T\u00fcbingen 72074 T\u00fcbingen Germany"},{"name":"Division of Vertebrate Paleontology Yale Peabody Museum of Natural History New Haven CT 06511 USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Kevin","family":"de Queiroz","sequence":"additional","affiliation":[{"name":"Department of Vertebrate Zoology National Museum of Natural History, Smithsonian Institution Washington DC 20560 USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Arhat","family":"Abzhanov","sequence":"additional","affiliation":[{"name":"Department of Organismic and Evolutionary Biology Harvard University Cambridge MA 02138 USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jacques A.","family":"Gauthier","sequence":"additional","affiliation":[{"name":"Department of Geology and Geophysics Yale University New Haven CT 06511 USA"},{"name":"Division of Vertebrate Paleontology Yale Peabody Museum of Natural History New Haven CT 06511 USA"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"311","published-online":{"date-parts":[[2013,9,16]]},"reference":[{"key":"e_1_2_4_2_1","doi-asserted-by":"publisher","DOI":"10.1038\/nature06991"},{"key":"e_1_2_4_3_1","doi-asserted-by":"publisher","DOI":"10.1080\/14772019.2011.558928"},{"key":"e_1_2_4_4_1","first-page":"89","article-title":"On the morphogeny of the carapace of the Testudinata","volume":"21","author":"Baur G.","year":"1887","journal-title":"Am. 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