Entotympanic

Last updated May 29, 2025

The entotympanic is a bone found in the ear region of many placental mammals. When present it forms the medioventral part of the auditory bulla; it is a neomorphic element derived from the tubal cartilage and the sheath of the tympanohyal. It is found in a wide variety of placental mammals, including Xenarthra, Afroinsectophilia, Hyracoidea, Pholidota, Carnivora, Perissodactyla, Chiroptera, Dermoptera, and Scandentia; it is (apparently secondarily) reduced or absent in Glires, Primates, Eulipotyphla, and Artiodactyla (including Cetacea).^[1] It is the only common neomorphic element of the mammalian skull.^[2]

The entotympanic contacts the ectotympanic, with which it makes up the auditory bulla.^[1]

References

1 2 Maier, Wolfgang (August 2013). "The entotympanic in late fetal artiodactyla (Mammalia)" . Journal of Morphology. 274 (8): 926–939. doi:10.1002/jmor.20149. ISSN 0362-2525.
↑ Koyabu, Daisuke (2023-07-03). "Evolution, conservatism and overlooked homologies of the mammalian skull". Philosophical Transactions of the Royal Society B: Biological Sciences. 378 (1880). doi:10.1098/rstb.2022.0081. ISSN 0962-8436. PMC 10184252 . PMID 37183902.

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[:0-1] 1 2 Maier, Wolfgang (August 2013). "The entotympanic in late fetal artiodactyla (Mammalia)" . Journal of Morphology. 274 (8): 926–939. doi:10.1002/jmor.20149. ISSN 0362-2525.

[2] Koyabu, Daisuke (2023-07-03). "Evolution, conservatism and overlooked homologies of the mammalian skull". Philosophical Transactions of the Royal Society B: Biological Sciences. 378 (1880). doi:10.1098/rstb.2022.0081. ISSN 0962-8436. PMC 10184252 . PMID 37183902.

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