Abstract
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.
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References
Beecher, R. M. (1977). Function and fusion at the mandibular symphysis.Am. J. Phys. Anthropol. 47: 325–336.
Beecher, R. M. (1979). Functional significance of the mandibular symphysis.J. Morphol. 159: 117–130.
Elliott, D. G. (1912). A review of the primates.Monogr. Am. Mus. Nat. Hist. I–III.
Gingerich, P. D. (1977). New species of Eocene primates and the phylogeny of European Adapidae.Folia Primtol. 28: 60–80.
Gingerich, P. D. (1979). Phylogeny of middle Eocene Adapidae (Mammalia, Primates) in North America:Smilodectes andNotharctus.J. Paleontol. 53: 153–163.
Gingerich, P. D., and Schoeninger, M. (1977). The fossil record and primate phylogeny.J. Hum. Evol. 6: 483–505.
Gingerich, P. D., and Simons, E. L. (1977). Systeniatics, phylogeny, and evolution of early Eocene Adapidae (Mammalia, Primates) in North America.Contr. Mus. Paleontol. Univ. Mich. 24(22): 245–279.
Gregory, W. K. (1920). On the structure and relations ofNotharctus, an American Eocene primate.Monogr. Am. Mus. Nat. Hist. 3(2): 49–243.
Kay, R. F. (1975). The functional adaptations of primate molar teeth.Am. J. Phys. Anthro-pol. 43: 195–216.
McKenna, M., Russell, D., West, R., Black, C, Turnbull, W., Dawson, M., and Lillegraven, J. (1973). K/Ar recalibration of Eocene North American land-mammal “ages” and European ages.Geol. Soc. Amer. Abstr. Prog. 5: 733.
Radinsky, L. (1977). Brains of early carnivores.Paleobiology 3: 333–349.
Rigler, L., and Mlinsek, B. (1968). Die Symphyse der Mandibula beim Rinde: Ein Beitrag zur Kenntnis ihrer Struktur und Funktion.Anat. Anz. 122: 293–314.
Robinson, P. (1957). The species ofNotharctus from the middle Eocene.Postilla 28: 1–23.
Scapino, R. P. (1965). The third joint of the canine jaw.J. Morphol. 116: 23–50.
Scapino, R. P. (1981). Morphological investigation into functions of the jaw symphysis in carnivores.J. Morphol. 167: 339–375.
Schoeninger, M. J. (1976). Functional significance of the development of a mesostyle in the Eocene primatesPelycodus andNotharctus.Am. J. Phys. Anthropol. 44: 204.
Simons, E. L. (1972).Primate Evolution: An Introduction to Man’s Place in Nature, Mac-millan, New York.
Stehlin, H. G. (1912). Die SÄugetiere des schweizerischen EocÄns. Critischer Catalog der Materialien, 7ter Thiel, erste Halfte.Adapts. Abh. Schweiz. PalÄontol. Ges. 41: 1299–1552.
Tattersall, I. (1973). Cranial anatomy of the Archaeolemurinae (Lemuroidea, Primates).Am. Mus. Nat. Hist. Anthropol. Papers 52(1): 1–110.
Vaughan, T. A. (1978).Mammalogy, W. B. Saunders, Philadelphia.
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Beecher, R.M. Evolution of the mandibular symphysis in Notharctinae (Adapidae, Primates). Int J Primatol 4, 99–112 (1983). https://doi.org/10.1007/BF02739362
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DOI: https://doi.org/10.1007/BF02739362