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Here, we present an exceptionally-preserved specimen of <jats:italic>Confuciusornis<\/jats:italic> which, through Laser-Stimulated Fluorescence imaging, is identified as preserving a disassociated rhamphotheca. Reconstruction of the in vivo position of the rhamphotheca validates the association of the rhamphotheca with two previous confuciusornithid specimens while calling that of a third specimen into question. The ease of dissociation is discussed and proposed with a fourth specimen alongside finite element analysis as evidence for preferential soft-food feeding. However, this proposition remains tentative until there is a better understanding of the functional role of beak attachment in living birds. Differences in post-rostral extent and possibly rhamphotheca curvature between confuciusornithids and modern birds hint at developmental differences between the two. Together, this information provides a wealth of new information regarding the nature of the beak outside crown Aves.<\/jats:p>","DOI":"10.1038\/s42003-020-01252-1","type":"journal-article","created":{"date-parts":[[2020,9,21]],"date-time":"2020-09-21T10:03:11Z","timestamp":1600682591000},"update-policy":"https:\/\/doi.org\/10.1007\/springer_crossmark_policy","source":"Crossref","is-referenced-by-count":16,"title":["Disassociated rhamphotheca of fossil bird Confuciusornis informs early beak reconstruction, stress regime, and developmental patterns"],"prefix":"10.1038","volume":"3","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-6467-0199","authenticated-orcid":false,"given":"Case Vincent","family":"Miller","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Michael","family":"Pittman","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7996-618X","authenticated-orcid":false,"given":"Thomas G.","family":"Kaye","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Xiaoli","family":"Wang","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9284-9591","authenticated-orcid":false,"given":"Jen A.","family":"Bright","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Xiaoting","family":"Zheng","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"297","published-online":{"date-parts":[[2020,9,21]]},"reference":[{"key":"1252_CR1","doi-asserted-by":"publisher","first-page":"679","DOI":"10.1038\/21411","volume":"399","author":"L Hou","year":"1999","unstructured":"Hou, L., Martin, L. 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