Bailey Katie E, Lad Susan E, Pampush James D
Department of Anthropology, Texas A&M University, College Station, Texas.
Department of Anthropology, University of Florida, Gainesville, Florida.
Am J Primatol. 2017 Jun;79(6). doi: 10.1002/ajp.22646. Epub 2017 Mar 3.
Most colobine monkeys primarily move through their arboreal environment quadrupedally. Douc langurs (Pygathrix spp.), however, are regularly observed to use suspensory behaviors at the Endangered Primate Rescue Center (EPRC) in Northern Vietnam. Previous work has linked variation in scapular morphology to different modes of primate arboreal locomotion. Here we investigate whether the shape of the Pygathrix scapula resembles obligate brachiators (gibbons) or obligate arboreal quadrupeds (other cercopithecoids). Using a MicroScribe G2X 3D digitizer, the positions of 17 landmarks were recorded on 15 different species of nonhuman primates (n = 100) from three categories of locomotor behavior: brachiator, arboreal quadruped, and unknown (Pygathrix). All analyses were conducted in the R package geomorph. A Procrustes analysis uniformly scaled the shape data and placed specimens into the same morphospace. A Principal Component Analysis was used to examine scapular shape and a Procrustes ANOVA was conducted to test for shape difference in the scapulae. A pairwise analysis was used to compare the means of the locomotor categories and identify any statistically significant differences. A phylogenetically controlled Procrustes ANOVA was also conducted using a phylogeny from 10kTrees. Results show Pygathrix scapular morphology is significantly different from both arboreal colobine quadrupeds (p < 0.01) and hylobatid brachiators (p < 0.01). It does, however, share some features with each including a long vertebral border, like other cercopithecoids, and a more laterally projecting acromion process, like the hylobatids. The principal difference segregating Pygathrix from both the arboreal quadrupeds and the brachiators is the more medially placed superior angle. These nuanced morphological characteristics associated with suspensory behaviors may be useful for inferring suspensory locomotion in the primate fossil record.
大多数疣猴主要以四足方式在其树栖环境中移动。然而，在越南北部的濒危灵长类动物救助中心（EPRC），经常观察到白臀叶猴（Pygathrix spp.）会使用悬垂行为。先前的研究将肩胛骨形态的变化与灵长类动物不同的树栖运动模式联系起来。在这里，我们研究白臀叶猴肩胛骨的形状是否类似于专性臂行者（长臂猿）或专性树栖四足动物（其他猕猴类）。使用MicroScribe G2X 3D数字化仪，在来自三种运动行为类别的15种不同的非人类灵长类动物（n = 100）上记录了17个地标点的位置：臂行者、树栖四足动物和未知类别（白臀叶猴）。所有分析均在R包geomorph中进行。普罗克汝斯忒斯分析对形状数据进行统一缩放，并将标本放入相同的形态空间。主成分分析用于检查肩胛骨形状，并进行普罗克汝斯忒斯方差分析以测试肩胛骨的形状差异。使用成对分析来比较运动类别均值并识别任何统计学上的显著差异。还使用来自10kTrees的系统发育进行了系统发育控制的普罗克汝斯忒斯方差分析。结果表明，白臀叶猴的肩胛骨形态与树栖疣猴四足动物（p < 0.01）和长臂猿科臂行者（p < 0.01）均有显著差异。然而，它确实与两者都有一些共同特征，包括像其他猕猴类一样的长脊椎边缘，以及像长臂猿科一样的更向外突出的肩峰突。将白臀叶猴与树栖四足动物和臂行者区分开来的主要差异是上角位置更偏向内侧。这些与悬垂行为相关的细微形态特征可能有助于推断灵长类化石记录中的悬垂运动。
