{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,5]],"date-time":"2026-10-05T22:00:00Z","timestamp":1791237600515,"version":"4.1.0"},"reference-count":32,"publisher":"Zoological Society of Japan","issue":"1","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Zoological Science"],"published-print":{"date-parts":[[2026,1,26]]},"abstract":"<jats:p>In tetrapod evolution, the middle ear evolved independently at least four times and represents key innovations for airborne hearing. As the tympanic membrane developed at the interface between the mandibular and hyoid arches, the evolution of middle ears likely involved modifications of jaw joint morphologies. The caudal end of the lower jaw in extant birds accompanies the medial and caudal processes, while the other extant diapsids possess a single process, namely the retroarticular process (RAP). The evolutionary process of these skeletal morphologies, however, remained unclear. Here we examined embryonic developments of the chicken, American alligator, and Chinese soft-shelled turtle, as well as the fossil record, to show that the medial process of the birds is homologous with the retroarticular process. During embryonic development of the chicken, the caudal end of the developing lower jaw became shifted medially, and subsequently the caudal process was secondarily formed. This fact together with the fossil data of Mesozoic theropods indicates that the medial process of the avian lower jaw would be homologous with the RAP. Based on our observations, the invagination of the external auditory meatus likely involves the infolding of the hyoid arch elements including the RAP. Considering the medially oriented RAP as an osteological correlate of the deep external auditory meatus seen in the extant birds, the deep ear canal can be traced back to the common ancestor of coelurosaurian dinosaurs.<\/jats:p>","DOI":"10.2108\/zs250108","type":"journal-article","created":{"date-parts":[[2026,1,21]],"date-time":"2026-01-21T05:28:42Z","timestamp":1768973322000},"page":"72-80","source":"Crossref","is-referenced-by-count":1,"title":["Evolution of the Jaw Joint and Middle Ear Morphologies in the Lineage Towards Birds"],"prefix":"10.2108","volume":"43","author":[{"given":"Takumi","family":"Watanabe","sequence":"first","affiliation":[{"name":"Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Fernando E.","family":"Novas","sequence":"additional","affiliation":[{"name":"Fundaci\u00f3n de Historia Natural \u201cF\u00e9lix de Azara\u201d, Hidalgo St at 775, 1405 Buenos Aires, Argentina"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Tatsuya","family":"Hirasawa","sequence":"additional","affiliation":[{"name":"Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"848","reference":[{"key":"19","doi-asserted-by":"crossref","unstructured":"DM Noden,  \"Dev Biol.\"  96, \"The role of the neural crest in patterning of avian cranial skeletal, connective, and muscle tissues.\" 144 (1983)","DOI":"10.1016\/0012-1606(83)90318-4"},{"key":"9","doi-asserted-by":"crossref","unstructured":"V Hamburger  and HL Hamilton  \"J Morphol.\"  88, \"A series of normal stages in the development of the chick embryo.\" 49 (1951)","DOI":"10.1002\/jmor.1050880104"},{"key":"1","doi-asserted-by":"crossref","unstructured":"EF Allin,  \"J Morphol.\"  147, \"Evolution of the mammalian middle ear.\" 403 (1975)","DOI":"10.1002\/jmor.1051470404"},{"key":"2","doi-asserted-by":"crossref","unstructured":"WJ Bock,  \"Auk.\"  77, \"Secondary articulation of the avian mandible.\" 19 (1960)","DOI":"10.2307\/4082382"},{"key":"3","doi-asserted-by":"crossref","unstructured":"M Bronzati, FM Vieceli, VS Botezelli, et al.  \"Curr Biol.\"  34, \"Deep-time origin of tympanic hearing in crown reptiles.\" 5334 (2024)","DOI":"10.1016\/j.cub.2024.09.041"},{"key":"4","doi-asserted-by":"crossref","unstructured":"G Capshaw, J Christensen-Dalsgaard, CE Carr,  \"J Exp Biol.\"  225, \"Hearing without a tympanic ear.\" jeb244372 (2022)","DOI":"10.1242\/jeb.244130"},{"key":"5","doi-asserted-by":"crossref","unstructured":"JA Clack,  \"J Neurobiol.\"  53, \"Patterns and processes in the early evolution of the tetrapod ear.\" 251 (2002)","DOI":"10.1002\/neu.10129"},{"key":"6","doi-asserted-by":"crossref","unstructured":"NG Crawford, JF Parham, AB Sellas, et al.  \"Mol Phylogenet Evol.\"  83, \"A phylogenomic analysis of turtles and their kin: an empirical comparison of coalescent and concatenation approaches.\" 250 (2015)","DOI":"10.1016\/j.ympev.2014.10.021"},{"key":"7","unstructured":"MWJ Ferguson,  \"Biology of the Reptilia, Vol. 14 (Development A).\"  \"The reproductive biology and embryology of the crocodilians.\" 330 (1985)"},{"key":"8","doi-asserted-by":"crossref","unstructured":"T Furutera, M Takechi, T Kitazawa, et al.  \"Development.\"  144, \"Differing contributions of the first and second pharyngeal arches to tympanic membrane formation in the mouse and chick.\" 3315 (2017)","DOI":"10.1242\/dev.149765"},{"key":"10","doi-asserted-by":"crossref","unstructured":"T Hirasawa, H Nagashima, S Kuratani,  \"Nat Commun.\"  4, \"The endoskeletal origin of the turtle carapace.\" 2107 (2013)","DOI":"10.1038\/ncomms3107"},{"key":"11","doi-asserted-by":"crossref","unstructured":"JA Hopson,  \"Am Zool.\"  6, \"The origin of the mammalian middle ear.\" 437 (1966)","DOI":"10.1093\/icb\/6.3.437"},{"key":"12","unstructured":"NN Iordansky,  \"Biology of the Reptilia, Vol. 4 (Morphology D).\"  \"The skull of the Crocodilia.\" 201 (1973)"},{"key":"13","doi-asserted-by":"crossref","unstructured":"WG Joyce, J Anquetin, EA Cadena, et al.  \"Swiss J Palaeontol.\"  140, \"A nomenclature for fossil and living turtles using phylogenetically defined clade names.\" 5 (2021)","DOI":"10.1186\/s13358-020-00211-x"},{"key":"15","doi-asserted-by":"crossref","unstructured":"M Laurin,  \"Ann Sci Nat Zool Biol Anim.\"  19, \"The importance of global parsimony and historical bias in understanding tetrapod evolution: Part I. 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