The First Mammals

  • Doris M. Kermack
  • Kenneth A. Kermack


The first mammals appear at the boundary between the Triassic and the Jurassic, most likely just before the end of the former period (see Table 3.1). Before describing them we must consider exactly what we mean by the term ‘mammal’. Quite clearly no single character by itself expresses the concept of a mammal. To most people a mammal means a warm-blooded furry animal, whose mother nourished it from birth with her milk, a secretion of the modified sebaceous glands called mammae. Such a definition is of little value to a palaeontologist with only fossils to study. Skeletal characters are clearly needed, since, except in exceptional circumstances, nothing else remains in a fossil. In modern mammals there is a chain of three bones or auditory ossicles (the malleus, incus and stapes), which conducts sounds across the middle ear from the tympanic membrane to the fenestra ovalis of the inner ear. In all other tetrapods there is but a single auditory ossicle — the stapes. The mammalian jaw joint is between the condyle on the dentary and the glenoid on the squamosal, which is in contrast to the articular-quadrate joint of the Amphibia and reptiles. The reptilian articular and quadrate have become the malleus and incus respectively of the Mammalia, where the lower jaw consists of but a single bone, the dentary, as against the many-boned lower jaw of the other tetrapods. There are other skeletal characters, such as the three phalanges in the digits of a mammal, which had already been acquired by some of the later mammal-like reptiles. So the palaeontologist is left with a choice of just two characters, which are to some extent correlated with each other.


Molar Tooth Cheek Tooth Main Cusp Auditory Ossicle Small Cusp 
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  1. Broili, F. and Schröder, J. (1934) ‘Zur Osteologie des Kopfes von Cynognathus’, Sitzungsber. Bay. Akad. Wiss. Math. Naturwiss., 95, 95–128Google Scholar
  2. Crompton, A. W. (1974) ‘The Dentitions and Relationships of the Southern African Triassic Mammals, Erythrotherium parringtoni and Megazostrodon rudnerae’, Bull. Brit. Mus. (nat. hist.), 24, 397–437Google Scholar
  3. Datta, P. M. (1981) ‘The First Jurassic Mammal from India’, Zool. J. Linn. Soc. Lond., 73, 307–12CrossRefGoogle Scholar
  4. Datta, P. M., Yadagiri, P. and Rao, B. R. J. (1978) ‘Discovery of Early Jurassic Micromammals from Upper Gondwana Sequence of Pranhita Godavari Valley, India’, J. Geol. Soc. India, 19, 64–8Google Scholar
  5. Jenkins, F. A. (1982) News Bulletin, 126, 74, Society of Vertebrate Palaentology, Gainsville, Florida, USAGoogle Scholar
  6. Kermack, D. M., Kermack, K. A. and Mussett, F. (1968) ‘The Welsh Pantothere Kuehneotherium praecursoris’, J. Linn. Soc. (Zool.), 47, 407–23Google Scholar
  7. Kermack, K. A. and Kielan-Jaworoayska, Z. (1971) ‘Therian and Non-therian mammals’ in Kermack D. M. and Kermack K. A. (eds.), Early Mammals, Zool. J. Linn. Soc., Lond., 50, Suppl.l, 103–15Google Scholar
  8. Kermack, K. A., Lees, P. M. and Mussett, F. (1965) Aegialodon dawsoni, a New Tuberculosectorial Tooth from the Lower Wealden’, Proc. Royal Soc. B., 162, 535–54CrossRefGoogle Scholar
  9. Kermack, K. A., Mussett, F. and Rigney, H. W. (1973) ‘The Lower Jaw of Morganucodon’, Zool. J. Linn. Soc., Lond., 53, 87–175Google Scholar
  10. Kermack, K. A., Mussett, F. and Rigney, H. W. (1981) ‘The Skull of Morganucodon’, Zool. J. Linn. Soc., Lond., 71, 1–158Google Scholar
  11. Kühne, W. G. (1956) The Liassic Therapsid Oligokyphus, Br. Mus. (nat. hist ), LondonGoogle Scholar
  12. Kühne, W. G. (1958) ‘Rhaetische Triconodonten aus Glamorgan, ihre Stellung zwischen den Klassen Reptilia und Mammalia und ihre Bedeutung für Reichart’sche Theorie’, Paläont. Zeit., series 5, 32, 197–235Google Scholar
  13. Parrington, F. R. (1947) ‘On a Collection of Rhaetic Mammalian Teeth’, Proc. Zool. Soc. Lond., 116, 707–28Google Scholar
  14. Rigney, H. W. (1963) ‘A Specimen of Morganucodon from Yunnan’, Nature, 197, 1122–3CrossRefGoogle Scholar
  15. Russell, D., Sigogneau-Russell, D. and Wouters, G. (1976) ‘Une Dent d’aspect Mammalien en Provenance du Rhétien Francais’, Géobios, 4, 377–92CrossRefGoogle Scholar
  16. Sigogneau-Russel], D. (1978) ‘Découverte de Mammifères Rhétiens (Trias Supérieur) dans l’est de la France’, C. R. Acad. Sc. Paris t. 287 série D, 991–3Google Scholar
  17. Sigogneau-Russell, D. (1983a) ‘A New Therian Mammal from the Rhaetic Locality of SaintNicolas-de Port (France)’, Zool. J. Linn. Soc., Lond., 78, 175–86CrossRefGoogle Scholar
  18. Sigogneau-Russell, D. (1983b) ‘Nouveaux taxons de Mammifères rhetiens’, Acta palaeont. polonica, Warsaw, 28, 233–49, plates 10–12Google Scholar
  19. Watson, D. M. S. (1911) ‘The Skull of Diademodon, with Notes on Those of Some Other Cynodonts’, Ann. Mag. Nat. Hist., ser. 8, 8, 293–330Google Scholar
  20. Young, C. C. (1978) ‘New Materials of Eozostrodon’, Vertebrata palasiatica, 16, 1–3Google Scholar

Copyright information

© Doris M. Kermack and Kenneth A. Kermack 1984

Authors and Affiliations

  • Doris M. Kermack
    • 1
  • Kenneth A. Kermack
    • 2
  1. 1.Department of Pure & Applied BiologyImperial CollegeLondonUK
  2. 2.Department of ZoologyUniversity College, LondonLondonUK

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