Congdon Kimberly A, Ravosa Matthew J
Department of Basic Sciences, College of Osteopathic Medicine, Touro University Nevada, Henderson, Nev., USA.
Folia Primatol (Basel). 2016;87(4):224-243. doi: 10.1159/000450641. Epub 2016 Oct 29.
Skeletal functional morphology in primates underlies many fossil interpretations. Understanding the functional correlates of arboreal grasping is central to identifying locomotor signatures in extinct primates. We tested 3 predictions linking substrate orientation and digital grasping pressures: (1) below-branch pressures are greater than above-branch and vertical-branch pressures; (2) there is no difference in pressure exerted across digits within autopods at any substrate orientation, and (3) there is no difference in pressure exerted between homologous digits across autopods at any substrate orientation. Adult males and females from 3 strepsirrhine species crossed an artificial arboreal substrate oriented for above-, below- and vertical-branch locomotion. We compared digital pressures within and across behaviors via ANOVA and Tukey's Honest Significant Difference test. Results show limited support for all predictions: below-branch pressures exceeded vertical-branch pressures and above-branch pressures for some digits and species (prediction 1), lateral digits often exerted greater pressures than medial digits (prediction 2), and pedal digits occasionally exerted greater pressures than manual digits during above-branch and vertical orientations but less often for below-branch locomotion (prediction 3). We observed functional variability across autopods, substrate and species that could underlie morphological variation within and across primates. Future work should consider the complexity of arboreality when inferring locomotor modes in fossils.
灵长类动物的骨骼功能形态是许多化石解释的基础。理解树栖抓握的功能相关性是识别已灭绝灵长类动物运动特征的核心。我们测试了3个将底物方向与手指抓握压力联系起来的预测：（1）树枝下方的压力大于树枝上方和垂直树枝的压力；（2）在任何底物方向上，自足内各手指施加的压力没有差异，以及（3）在任何底物方向上，自足间同源手指施加的压力没有差异。来自3种原猴亚目物种的成年雄性和雌性穿过了一个为树枝上方、下方和垂直树枝运动而设置的人工树栖底物。我们通过方差分析和图基诚实显著差异检验比较了不同行为内和不同行为间的手指压力。结果显示对所有预测的支持有限：对于某些手指和物种，树枝下方的压力超过了垂直树枝的压力和树枝上方的压力（预测1），外侧手指通常比内侧手指施加更大的压力（预测2），并且在树枝上方和垂直方向运动时，足部手指偶尔比手部手指施加更大的压力，但在树枝下方运动时这种情况较少（预测3）。我们观察到自足、底物和物种之间的功能变异性，这可能是灵长类动物内部和之间形态变异的基础。在推断化石的运动模式时，未来的研究应该考虑树栖生活的复杂性。
