Humeral and Femoral Diaphyseal Cross-Sectional Geometry and Articular Dimensions in Prosimii and Platyrrhini (primates) With Application for Reconstruction of Body Mass and Locomotor Behavior in Adapidae (primates: Eocene)

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Abstract

The objective of this study is to examine the relationship between humeral and femoral diaphyseal cross-sectional and articular properties and body mass and locomotory specialization in extant small primates (less than 7500 grams). Results from this study of modern primates are applied to the Eocene family Adapidae, fossil primates of similar body size and postcranial morphology, to reconstruct locomotory behavior and estimate body mass.

The extant primate analysis indicates that small primates specialized for leaping and bipedal hopping have greater femoral rigidity and femoral length, and larger femoral articulations than do less specialized primates. Small primates specialized for slow climbing are characterized by relatively greater rigidity, particularly axial rigidity, in both the humerus and femur than are less specialized primates. Analysis of allometric trends in extant small primates indicates that most humeral and femoral properties scale with slight positive allometry with respect to body mass.

From comparison with the modern primate results, notharctine femoral rigidity indicates that notharctines were not specialized leapers, but were only slightly more saltatory than modern nonspecialized quadrupeds. Patterns of adapine diaphyseal rigidity and femoral length suggest that adapines were powerful climbers, although not as specialized for this behavior as are modern slow climbers. Both notharctine and adapine distal humeral articular proportions indicate that adapid quadrupedalism may have involved less parasagittal elbow movement, and more vertical climbing, than seen in more frequent above-branch walkers.

Adapid body masses are reconstructed using cross-sectional property formulae based on the modern comparative sample. For most Notharctus tenebrosus and Smilodectes gracilis, these mass estimates are between 2200-3000 grams. The mass distribution for Adapis is bimodal, with one cluster of individuals between 1500- 2500 grams, and the other between 3000-4000 grams. This suggests that more than one species is represented in the sample.

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Cited By (3)

Year	Entry
1995	Heinrich RE. Functional Morphology and Body Size of Early Tertiary Miacoidea (mammalia, Carnivora) [PhD thesis]. Johns Hopkins University; 1995.
1999	Egi N. Functional Morphology of the Limb Bones in Recent Carnivores and Its Application to North American Hyaenodontid Creodonta [PhD thesis]. Johns Hopkins University; 1999.
2007	Organ JM. The Functional Anatomy of Prehensile and Nonprehensile Tails of the Platyrrhini (primates) and Procyonidae (carnivora) [PhD thesis]. Johns Hopkins University; September 2007.