初期の四肢動物では噴水孔は耳切痕（英語版）となり、未だ呼吸の機能を担っていたと推測される。これは現生の四肢動物では耳管となり、呼吸の機能は失ったものの口腔との接続を保っている[11][12][13]。
脚注^ Graham, Jeffrey B.; Wegner, Nicholas C.; Miller, Lauren A.; Jew, Corey J.; Chin Lai, N.; Berquist, Rachel M.; Frank, Lawrence R.; Long, John A. (2014). “Spiracular air breathing in polypterid fishes and its implications for aerial respiration in stem tetrapods”. Nature Communications 5: 3022. doi:10.1038/ncomms4022. .mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .citation.cs-ja1 q,.mw-parser-output .citation.cs-ja2 q{quotes:"「""」""『""』"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free a,.mw-parser-output .citation .cs1-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/6/65/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited a,.mw-parser-output .id-lock-registration a,.mw-parser-output .citation .cs1-lock-limited a,.mw-parser-output .citation .cs1-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/d/d6/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription a,.mw-parser-output .citation .cs1-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/a/aa/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url("//upload.wikimedia.org/wikipedia/commons/4/4c/Wikisource-logo.svg")right 0.1em center/12px no-repeat}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:#d33}.mw-parser-output .cs1-visible-error{color:#d33}.mw-parser-output .cs1-maint{display:none;color:#3a3;margin-left:0.3em}.mw-parser-output .cs1-format{font-size:95%}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}PMID 24451680. 
^ Romer, A.S. (1949): The Vertebrate Body. W.B. Saunders, Philadelphia. (2nd ed. 1955; 3rd ed. 1962; 4th ed. 1970)
^ Romer, Alfred Sherwood; Parsons, Thomas S. (1977). The Vertebrate Body. Philadelphia, PA: Holt-Saunders International. pp. 316?327. ISBN 0-03-910284-X 
^ “Will a Shark Drown if It Stops Moving?” (英語). HowStuffWorks (2008年6月9日). 2021年5月18日閲覧。
^ “A list of sharks that are obligate ram ventilators :: Sacha Chua”. sachachua.com. 2021年5月18日閲覧。
^ Encyclopedia of Fishes. San Diego: Academic Press. (1998). pp. 69. ISBN 0-12-547665-5 
^ Graham, Jeffrey B.; Wegner, Nicholas C.; Miller, Lauren A.; Jew, Corey J.; Lai, N. Chin; Berquist, Rachel M.; Frank, Lawrence R.; Long, John A. (2014-01-23). “Spiracular air breathing in polypterid fishes and its implications for aerial respiration in stem tetrapods” (英語). Nature Communications 5 (1): 3022. doi:10.1038/ncomms4022. ISSN 2041-1723. https://www.nature.com/articles/ncomms4022. 
^ Clack, Jennifer A. (2012-06-27) (英語). Gaining Ground, Second Edition: The Origin and Evolution of Tetrapods. Indiana University Press. ISBN 978-0-253-00537-3. https://books.google.com/books?id=4j9AKGsQ1msC&q=%22spiracular+chamber+is+closed+in+coelacanths%22&pg=PA391 
^ Burggren, W. W. (August 1978). “Gill ventilation in the sturgeon, Acipenser transmontanus: unusual adaptations for bottom dwelling”. Respiration Physiology 34 (2): 153?170. doi:10.1016/0034-5687(78)90025-7. ISSN 0034-5687. PMID 30128. 
^ “Read the eBook Commissioners' report by Ontario. Game and fish commission online for free (page 37 of 41)”. www.ebooksread.com. 2021年5月18日閲覧。
^ Lombard, R. Eric; Bolt, John R. (1979). “Evolution of the tetrapod ear: an analysis and reinterpretation” (英語). Biological Journal of the Linnean Society 11 (1): 19?76. doi:10.1111/j.1095-8312.1979.tb00027.x. ISSN 1095-8312. https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1095-8312.1979.tb00027.x. 
^ “ ⇒Hearing in Stegocephalians”. tolweb.org. 2021年5月18日閲覧。
^ “Eustachian Tube Dysfunction: Treatment, Causes, Surgery & Healing Time” (英語). MedicineNet. 2021年5月18日閲覧。