Forelimb compliance in arboreal and terrestrial opossums

Primates display high forelimb compliance (increased elbow joint yield) compared to most other mammals. Forelimb compliance, which is especially marked among arboreal primates, moderates vertical oscillations of the body and peak vertical forces and may represent a basal adaptation of primates for locomotion on thin, flexible branches. However, Larney and Larson (Am J Phys Anthropol 125 [2004] 42-50) reported that marsupials have forelimb compliance comparable to or greater than that of most primates, but did not distinguish between arboreal and terrestrial marsupials. If forelimb compliance is functionally linked to locomotion on thin branches, then elbow yield should be highest in marsupials relying on arboreal substrates more often. To test this hypothesis, we compared forelimb compliance between two didelphid marsupials, Caluromys philander (an arboreal opossum relying heavily on thin branches) and Monodelphis domestica (an opossum that spends most of its tin?? ground). Animals were videorecorded while ?? a runway or a horizontal 7-mm pole. Caluro?? higher elbow yield (greater changes in degree ?? flexion) on both substrates, similar to that r?? arboreal primates. Monodelphis was chara?? lower elbow yield that was intermediate b?? values reported by Larney and Larson (A?? Anthropol 125 [2004] 42-50) for more terr?? mates and rodents. This finding adds evidence ?? suggesting a functional link between arbore ??ticularly locomotion on thin, flexible bra?? forelimb compliance. These data add anoth?? gent trait between arboreal primates, Calu?? other arboreal marsupials and support the ?? that all primates evolved from a common an?? was a fine-branch arborealist. Copyright John Wiley & Sons. Reproduced with permission. An electronic version of this article is available online at http://www.interscience.wiley.com