Evolution of the Auditory System in Synapsida (“Mammal-Like Reptiles” and Primitive Mammals) as Seen in the Fossil Record

  • Edgar F. Allin
  • James A. Hopson


Based on evidence from comparative anatomy, embryology, and paleontology, it is well established that the middle ear of existing mammals is morphologically unique, the tympanic bone, malleus, incus, and tensor tympani muscle all being homologous with components of the feeding apparatus of other vertebrates (Fig. 28.1, see below for details). Extant mammals are also unique in having a very elongate cochlea, and sensitivity to a broader range of sound frequencies than other vertebrates, usually extending beyond 10,000 Hz. In addition, they are distinctive in generally having a protruding pinna (auricle) and a long, tubular external auditory meatus. The present chapter examines the extensive fossil evidence concerning the nature of the auditory machinery of early mammals and their antecedents. Both authors of the present account have written on this subject, arriving at different initial interpretations in certain regards (Hop-son 1966; Allin 1975).


Tympanic Membrane External Auditory Meatus Otic Capsule Dorsal Process Paroccipital Process 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Aitkin LM, Johnstone BM (1972) Middle ear function in a monotreme: the echidna (Tachyglossus aculeatus). J Exp Zool 180:245–250.PubMedCrossRefGoogle Scholar
  2. Allin EF (1975) Evolution of the mammalian middle ear. J Morph 147:403–438.PubMedCrossRefGoogle Scholar
  3. Allin EF (1986) The auditory apparatus of advanced mammal-like reptiles and early mammals. In: Hotton N III, McLean PD, Roth JJ, Roth EC (eds) The Ecology and Biology of Mammal-like Reptiles. Washington DC: Smithsonian Institution Press, pp. 283–294.Google Scholar
  4. Barghusen HR (1968) The lower jaw of cynodonts (Reptilia, Therapsida) and the evolutionary origin of mammal-like adductor jaw musculature. Postilla 116: 1–49.Google Scholar
  5. Barghusen HR (1972) The origin of the mammalian jaw apparatus. In: Schumacher GH (ed) Morphology of the Maxillo-Mandibular Apparatus. Leipzig: Thieme, pp. 26–32.Google Scholar
  6. Barghusen HR (1986) On the evolutionary origin of the therian tensor veli palatini and tensor tympani muscles. In: Hotton N III et al. (eds) The Ecology and Biology of Mammal-like Reptiles. Washington DC: Smithsonian Institution Press, pp. 253–262.Google Scholar
  7. Barry TH (1968) Sound conduction in the fossil anomodont Lystrosaurus, Ann S Afr Mus 50:275–281.Google Scholar
  8. Chudinov PK (1965) New facts about the upper Permian of the U.S.S.R. J Geol 73:117–130.CrossRefGoogle Scholar
  9. Cox CB (1959) On the anatomy of a new dicynodont genus with evidence on the position of the tympanum. Proc Zool Soc Lond 132:697–750.Google Scholar
  10. Cox CB (1962) A natural cast of the inner ear of a dicynodont. Am Mus Novitates 2116:1–6.Google Scholar
  11. Crompton AW (1972) The evolution of the jaw articulation of cynodonts. In: Joysey KA, Kemp TS (eds) Studies in Vertebrate Evolution. Edinburgh: Oliver and Boyd, pp. 231–251.Google Scholar
  12. Crompton AW (1985) Origin of the temporomandibular joint. In: Carlson DS, McNamara JA, Ribbens KA (eds) Developmental Aspects of Temporomandibular Joint Disorders. Monograph 16, Craniofacial Growth Series, Center for Human Growth and Development, U. Mich., Ann Arbor, pp. 1–18. Google Scholar
  13. Crompton AW (1989) The evolution of mammalian mastication. In: Wake DB, Roth G (eds) Complex Organismal Functions: Integration and Evolution in Vertebrates. New York: Wiley and Sons, pp. 23–40.Google Scholar
  14. Crompton AW, Sun A (1985) Cranial structure and relationships of the Liassic mammal Sinoconodon. Zool J Linn Soc 85:99–119.CrossRefGoogle Scholar
  15. De Beer GR (1937) The Development of the Vertebrate Skull. Oxford: Clarendon Press.Google Scholar
  16. Estes R (1961) Cranial anatomy of the cynodont reptile Thirinaxodon liorhinus. Bull Mus Comp Zool 6: 165–180.Google Scholar
  17. Fleischer G (1973) Studien am Skelett des Gehörorgans der Säugetiere, einschließlich des Menschen. Säugetierkundl Mitt 40:131–239.Google Scholar
  18. Fleischer G (1976) Hearing in extinct cetaceans as determined by cochlear structure. J Paleont 50:133–152.Google Scholar
  19. Fleischer G (1978) Evolutionary principles of the mammalian middle ear. Adv Anat Embryol Cell Biol 55: 1–70.Google Scholar
  20. Fourie S (1974) The cranial morphology of Thrinaxodon liorhinus Seeley. Ann S Afr Mus 65:337–400.Google Scholar
  21. Gaupp E (1913) Die Reichertsche Theorie. Arch Anat u Physiol Abt Anat Supplement 4:1–417.Google Scholar
  22. Goodrich ES (1930) Studies on the Structure and Development of Vertebrates. London: Macmillan.Google Scholar
  23. Gow CE (1986) A new skull of Megazostrodon (Mammalia, Triconodonta) from the Elliot Formation (Lower Jurassic) of southern Africa. Palaeont Afr 26:13–23.Google Scholar
  24. Graybeal A, Rosowski JJ, Ketten DR, Crompton AW (1989) Inner-ear structure in Morganucodon, an early Jurassic mammal. Zool J Linn Soc 96:107–117.CrossRefGoogle Scholar
  25. Gregory WK (1910) The orders of mammals. Bull Am Mus Nat Hist 27:1–524.Google Scholar
  26. Hopson JA (1966) The origin of the mammalian middle ear. Am Zool 6:437–450.PubMedGoogle Scholar
  27. Hopson JA (1987) The mammal-like reptiles: a study of transitional fossils. Am Biol Teacher 49:17–26.Google Scholar
  28. Hopson JA, Barghusen HR (1986) An analysis of therapsid relationships. In: Hotton N III et al. (eds) The Ecology and Biology of Mammal-like Reptiles. Washington, DC: Smithsonian Institution Press, pp. 83–106.Google Scholar
  29. Jenkins FA Jr, Crompton AW, Downs WR (1983) Mesozoic mammals from Arizona: New evidence on mammalian evolution. Science 222:1233–1235.PubMedCrossRefGoogle Scholar
  30. Kemp TS (1969) On the functional morphology of the gorgonopsid skull. Phil Trans Roy Soc Lond B 256:1–83.CrossRefGoogle Scholar
  31. Kemp TS (1972) The jaw articulation and musculature of the whaitsiid Therocephalia. In: Joysey KA, Kemp TS (eds) Studies in Vertebrate Evolution. Edinburgh:Oliver and Boyd, pp. 213–230. Google Scholar
  32. Kemp T (1979) The primitive cynodont Procynosuchus: Functional anatomy of the skull and relationships. Phil Trans Roy Soc Lond B 285:73–122.CrossRefGoogle Scholar
  33. Kemp TS (1982) Mammal-like Reptiles and the Origin of Mammals. London: Academic Press. Google Scholar
  34. Kermack KA (1963) The cranial structure of triconodonts. Phil Trans Roy Soc Lond B 246:83–102.CrossRefGoogle Scholar
  35. Kermack KA (1982) The ear in the Theropsida. Geobios mem spec 6:151–156.CrossRefGoogle Scholar
  36. Kermack KA, Mussett F (1983) The ear in mammal-like reptiles and early mammals. Acta Palaeontologica 28:147–158.Google Scholar
  37. Kermack KA, Mussett F, Rigney HW (1981) The skull of Morganucodon. Zool J Linn Soc 71:1–158.CrossRefGoogle Scholar
  38. Krebs B (1971) Evolution of the mandible and lower dentition in dryolestids (Pantotheria, Mammalia). Zool J Lin Soc Suppl 1, 50:89–102.Google Scholar
  39. Krebs B (1988) Mesozoiche Säugetiere-Ergebnisse von Ausgrabungen in Portugal. Sber Ges Naturf Freunde Berlin 28:95–107.Google Scholar
  40. Kühne WG (1956) The Liassic therapsid Oligokyphus. London: Brit Mus (Nat Hist).Google Scholar
  41. Maier W (1990) Phylogeny and ontogeny of mammalian middle ear structures. Neth J Zool 40:55–75.CrossRefGoogle Scholar
  42. Miao D (1988) Skull morphology of Lambdopsalis bulla (Mammalia, Multituberculata) and its implications to mammalian evolution. Contrib Geol Univ Wyoming Spec Pap 4:1–104.Google Scholar
  43. Miao D, Lillegraven JA (1986) Discovery of three ear ossicles in a multituberculate mammal. Nat Geog Res 2:500–507.Google Scholar
  44. Novacek MJ (1977) Aspects of the problem of variation, origin and evolution of the eutherian auditory bulla. Mamm Rev 7:131–149.CrossRefGoogle Scholar
  45. Olson EC (1944) Origin of mammals based upon cranial morphology of the therapsid suborders. Geol Soc Amer Spec Pap 55:1–136.Google Scholar
  46. Parrington FR (1946) On the cranial anatomy of some gorgonopsids and the synapsid middle ear. Proc Zool Soc Lond 125:1–40.Google Scholar
  47. Presley R (1984) Lizards, mammals and the primitive tetrapod tympanic membrane. Symp Zool Soc Lond No. 52:127–152.Google Scholar
  48. Pritchard U (1881) The cochlea of the Ornithorhynchus platypus compared with that of ordinary mammals and birds. Phil Trans Roy Soc Lond 172:267–282.CrossRefGoogle Scholar
  49. Quiroga JC (1979) The inner ear of two cynodonts (Reptilia—Therapsida) and some comments on the evolution of the inner ear from pelycosaurs to mammals. Gegenbaurs Morph Jahrb Leipzig 125:178–190.Google Scholar
  50. Reisz RR (1986) Pelycosauria. Handb Paläoherpetologie 17A:102.Google Scholar
  51. Romer AS (1970) The Chañares (Argentina) Triassic reptile fauna, VI. A chiniquodontid cynodont with an incipient squamosal-dentary jaw articulation. Breviora Mus Comp Zool No 344.Google Scholar
  52. Romer AS, Price LI (1940) Review of the Pelycosauria. Geol Soc Am Spec Pap 28:1–538.Google Scholar
  53. Rowe T (1988) Definition, diagnosis, and origin of Mammalia. J Vert Paleont 8:241–262.CrossRefGoogle Scholar
  54. Shute CCD (1956) The evolution of the mammalian eardrum and tympanic cavity. J Anat 90:261–281.PubMedGoogle Scholar
  55. Sigogneau D, Tchudinov PK (1972) Reflections on some Russian eotheriodonts (Reptilia, Synapsida, Therap-sida). Palaeovert 5:79–109.Google Scholar
  56. Sigogneau D (1974) The inner ear of Gorgonops (Reptilia, Therapsida, Gorgonopsia). Ann S Afr Mus 64:53–69.Google Scholar
  57. Simpson GG (1933) The ear region and the foramina of the cynodont skull. Am J Sei 26:285–294.Google Scholar
  58. Sues H-D (1985) The relationships of the Tritylodontidae (Synapsida). Zool J Linn Soc 85:205–217.CrossRefGoogle Scholar
  59. Sues H-D (1986) The skull and dentition of two tritylodontid synapsids from the Lower Jurassic of western North America. Bull Mus Comp Zool 151:217–268.Google Scholar
  60. Tumarkin A (1955) On the evolution of the auditory conducting apparatus: A new theory based on functional considerations. Evol 9:221–242.CrossRefGoogle Scholar
  61. Watson DMS (1913) Further notes on the skull, brain, and organs of special sense of Diademodon. Ann Mag Nat Hist 12:217–228.Google Scholar
  62. Watson DMS (1953) Evolution of the mammalian ear. Evol 7:159–177.CrossRefGoogle Scholar
  63. Westoll TS (1943) The hyomandibular of Eusthenopteron and the tetrapod middle ear. Proc Roy Soc Lond B 131:393–414.CrossRefGoogle Scholar
  64. Westoll TS (1945) The mammalian middle ear. Nature (London) 155:114–115.CrossRefGoogle Scholar

Copyright information

© Springer-Verlag New York Inc. 1992

Authors and Affiliations

  • Edgar F. Allin
  • James A. Hopson

There are no affiliations available

Personalised recommendations