Yapuncich Gabriel S, Seiffert Erik R, Boyer Doug M
Department of Evolutionary Anthropology, Duke University, Durham, North Carolina.
Department of Cell and Neurobiology, Keck School of Medicine, University of Southern California, Los Angeles, California.
Am J Phys Anthropol. 2017 Jun;163(2):367-406. doi: 10.1002/ajpa.23213. Epub 2017 Mar 27.
On the talus, the position and depth of the groove for the flexor hallucis longus tendon have been used to infer phylogenetic affinities and positional behaviors of fossil primates. This study quantifies aspects of the flexor hallucis longus groove (FHLG) to test if: (1) a lateral FHLG is a derived strepsirrhine feature, (2) a lateral FHLG reflects inverted and abducted foot postures, and (3) a deeper FHLG indicates a larger muscle.
We used linear measurements of microCT-generated models from a sample of euarchontans (n = 378 specimens, 125 species) to quantify FHLG position and depth. Data are analyzed with ANOVA, Ordinary and Phylogenetic Generalized Least Squares, and Bayesian Ancestral State Reconstruction (ASR).
Extant strepsirrhines, adapiforms, plesiadapiforms, dermopterans, and Ptilocercus exhibit lateral FHLGs. Extant anthropoids, subfossil lemurs, and Tupaia have medial FHLGs. FHLGs of omomyiforms and basal fossil anthropoids are intermediate between those of strepsirrhines and extant anthropoids. FHLG position has few correlations with pedal inversion features. Relative FHLG depth is not significantly correlated with body mass. ASRs support a directional model for FHLG position and a random walk model for FHLG depth.
The prevalence of lateral FHLGs in many non-euprimates suggests a lateral FHLG is not a derived strepsirrhine feature. The lack of correlations with pedal inversion features suggests a lateral FHLG is not a sufficient indicator of strepsirrhine-like foot postures. Instead, a lateral FHLG may reduce the risk of tendon displacement in abducted foot postures on large diameter supports. A deep FHLG does not indicate a larger muscle, but likely reduces bowstringing during plantarflexion.
在距骨上，拇长屈肌腱沟的位置和深度已被用于推断化石灵长类动物的系统发育亲缘关系和姿势行为。本研究对拇长屈肌腱沟（FHLG）的各方面进行量化，以检验：（1）外侧FHLG是否是一种衍生的原猴亚目特征；（2）外侧FHLG是否反映足部内翻和外展姿势；（3）更深的FHLG是否表明肌肉更大。
我们对真灵长总目样本（n = 378个标本，125个物种）的微型计算机断层扫描（microCT）生成模型进行线性测量，以量化FHLG的位置和深度。数据采用方差分析、普通和系统发育广义最小二乘法以及贝叶斯祖先状态重建（ASR）进行分析。
现存的原猴亚目动物、兔猴类、近猴类、皮翼目动物和笔尾树鼩表现出外侧FHLG。现存的类人猿、亚化石狐猴和树鼩有内侧FHLG。始镜猴类和基础化石类人猿的FHLG介于原猴亚目动物和现存类人猿之间。FHLG位置与足部内翻特征几乎没有相关性。相对FHLG深度与体重没有显著相关性。ASR支持FHLG位置的定向模型和FHLG深度的随机游走模型。
许多非真灵长类动物中外侧FHLG的普遍存在表明外侧FHLG不是一种衍生的原猴亚目特征。与足部内翻特征缺乏相关性表明外侧FHLG不是类似原猴亚目足部姿势的充分指标。相反，外侧FHLG可能会降低在大直径支撑物上外展足部姿势时肌腱移位的风险。较深的FHLG并不表明肌肉更大，但可能会减少跖屈时的弓弦效应。
