Miniaturisation and the Origin of Mammals

Probably the most awkward abstract to read that I have ever seen because of the included references.

Bonaparte, J. F. 2011. Miniaturisation and the origin of mammals. Historical Biology (first published online, May 24, 2011). DOI: 10.1080/08912963.2011.559079.

Abstract - In this paper, the hypothesis of miniaturisation to explain the origin of mammals (Rowe 1993, Mammals phylogeny: mesozoic differentiation, multituberculates, monotremes, early therians, and marsupials. New York: Springer-Verlag, p. 129-145) is discussed, based on three lines of evidence resulting from new discoveries of eucynodonts in the Late Triassic of Southern Brazil (Bonaparte et al. 2003, Rev Bras Paleont 5:5-27; 2005, Rev Bras Paleont 8:25-46; 2006, New Mexico Museum Nat Hist Sci Bull 37:1-8; 2010, Rev Bras Paleont) that are: (1) the incomplete fossil record of eucynodonts known until 2003; (2) the structure of the primary palate rejects the ancestral condition of thrinaxodontids, probainognathids, chiniquodontids and cynognathids to the earliest mammals; and (3) the relatively large postdentary bones of the Middle Triassic brasilodontids that are otherwise very small in size (skull 44 mm long) suggest that small size per se did not help to improve the middle ear or other sophisticated organs present in the earliest mammals (Rowe 1993; Kemp 2005, The origin and evolution of mammals. Oxford University Press, p. 1-391). Small size possibly was not a secondary character, but a persistent primitive one. This new interpretation has resulted from comparative study of non-mammalian eucynodonts discovered in the Middle and Late Triassic of Brazil and those known previously. The general acceptance of the hypothesis of miniaturisation is thus a consequence of the poor fossil record of Middle and Late Triassic eucynodonts before 2003.


  1. Unfortunately the body of the paper is no easier!

  2. Since when is it practice to include references in the body of the abstract? Btw, if you have a PDF of this paper, I would appreciate it if you could email me it. Marshall does not subscribe to any of the providers which carry Historical Biology and I'd really like to read another Bonaparte paper ;)

    -Nick Gardner


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