International Journal of Primatology

, Volume 4, Issue 1, pp 99–112

Evolution of the mandibular symphysis in Notharctinae (Adapidae, Primates)


  • Robert M. Beecher
    • Department of AnatomyWright State University

DOI: 10.1007/BF02739362

Cite this article as:
Beecher, R.M. Int J Primatol (1983) 4: 99. doi:10.1007/BF02739362


The Eocene Notharctinae provide a record of increasing fusion of the mandibular symphysis. The two sympatric genera,Notharctus andSmilodectes, differed through time in two respects.Notharctus increased in body size and evolved a partially fused mandibular symphysis.Smilodectes changed little in body size and retained an unfused symphysis. Similarities in molar morphology between these two genera and extant leaf-eating mammals suggest thatNotharctus andSmilodectes were specialized for folivory, a dietary regime correlated with partial symphyseal fusion in many extant mammals. It is concluded that the presence and the extant of symphyseal fusion is a function of body size, diet, and jaw mechanics, complicated by lineagespecific factors that vary among higher mammalian taxa.

Key words

mandibular symphysisfossilsNotharctinae
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© Plenum Publishing Corporation 1983