Interdepartmental Doctoral Program in Anthropological Sciences, Stony Brook University, Stony Brook, New York 11794, USA.
J Hum Evol. 2009 Dec;57(6):721-31. doi: 10.1016/j.jhevol.2009.06.008. Epub 2009 Sep 17.
The first metatarsal of living Primates is characterized by a well-developed peroneal process, which appears proportionally larger in prosimians than in anthropoids. A large peroneal process has been hypothesized to: 1) reflect powerful hallucal grasping, 2) act as a buttress to reduce strain from loads acting on the entocuneiform-first metatarsal joint during landing and grasping after a leap, and/or 3) correlate with differences in physiological abduction of the hallux. In this study, we address the latter two hypotheses by comparing the morphology of the peroneal process in 143 specimens representing 37 species of extant prosimians, platyrrhine anthropoids, and tupaiids (tree shrews) that engage in different locomotor behaviors. In particular, we compare taxa that vary in leaping frequency and hallucal abduction. Linear and angular measurements on the first metatarsal were obtained to evaluate differences in relative peroneal process thickness and length, first metatarsal abduction angle, and overall first metatarsal shape. Leaping frequency was significantly correlated only with relative peroneal process thickness within extant lorisoids. Relative process length was positively correlated with the angle of hallucal abduction within prosimians; this angle is significantly greater in prosimians than anthropoids. Multivariate analyses of metatarsal shape effectively separate species along phylogenetic lines, but not by locomotor behaviors. The hypothesis that the peroneal process on the first metatarsal reduces the loads on the entocuneiform-first metatarsal joint during landing after a leap is in part supported by data from extant lorisoids (i.e., slow quadrupedal lorises vs. leaping galagos). A peroneal process of greater length within prosimians may serve to increase the lever arm for the peroneus longus muscle in order to prevent hyper-abduction, followed by inversion in locomotor situations where the animal's weight is born on a highly divergent/abducted hallux.
灵长类动物的第一跖骨的特征是具有发达的腓骨侧突，在原猴中比在人猿中比例更大。大的腓骨侧突被假设为：1）反映强大的脚趾抓握力，2）作为支撑物，以减少在着陆和跳跃后抓握时作用于中楔骨-第一跖骨关节的负荷引起的应变，和/或 3）与大脚趾的生理外展差异相关。在这项研究中，我们通过比较代表 37 种现存原猴、阔鼻猴和树鼩（树栖松鼠）的 143 个标本的腓骨侧突形态来检验后两个假设，这些物种从事不同的运动行为。特别是，我们比较了在跳跃频率和脚趾外展方面有所不同的分类群。对第一跖骨进行线性和角度测量，以评估相对腓骨侧突厚度和长度、第一跖骨外展角度和整体第一跖骨形状的差异。跳跃频率仅与现存懒猴科的相对腓骨侧突厚度显著相关。相对侧突长度与原猴类的脚趾外展角度呈正相关；该角度在原猴中明显大于人猿。跖骨形状的多元分析有效地沿着系统发育线分离物种，但不能通过运动行为进行分离。腓骨侧突在第一跖骨上减少跳跃后着陆时对中楔骨-第一跖骨关节的负荷的假设部分得到了现存懒猴科（即，缓慢的四足懒猴与跳跃的夜猴）的数据支持。原猴类中腓骨侧突更长，可能是为了增加腓骨长肌的杠杆臂，以防止在动物体重承受高度外展/外旋的大脚趾的运动情况下过度外展。
