A resampling approach and implications for estimating the phalangeal index from unassociated hand bones in fossil primates.
A resampling approach and implications for estimating the phalangeal index from unassociated hand bones in fossil primates.
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DOI：
10.1002/ajpa.22278
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发表时间：
2013-06
影响因子：
2.8
通讯作者：
V. Venkataraman;C. Rolian;A. Gordon;B. Patel
中科院分区：
文献类型：
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作者：
V. Venkataraman;C. Rolian;A. Gordon;B. Patel
灵长类动物化石组合通常有掌骨和指骨，从中可以推断出功能/行为的解释。例如，固有手的比例可以表明手的功能和底物的使用。但是，从不相关的手元素估计内在手的比例可能是不完美的，由于数字错误归因。虽然分离的掌骨可以识别到一个特定的手指，指骨很难分配到一个特定的射线。我们使用重新抽样的方法来评估如何估计内在手的比例是由这种不确定性的影响。首先，对陆生、半陆生和树栖分类群的相关标本计算第三指的指骨指数——中间指骨长度加上近端指骨长度除以掌骨长度。然后，我们使用重采样程序生成基于重采样比率的“复合指”分布，其中随机选择来自第二，第四和第五射线以及不同个体的指骨。结果证实，指骨指数相关的第三指显著区分群体。我们还发现，重采样比率的平均值明显较低，表明使用复合数字容易出现系统性低估。重新采样的比率也产生了更大的分布差异，这使得类群之间的差异变得模糊，尽管大多数树栖和陆栖类群之间仍然存在显著差异。我们的结论是，使用不相关的指骨来计算指骨指数容易产生抽样偏差。然而，重新采样方法有可能为化石分类群的手部比例估计提供信息，前提是比较样本必须模拟化石组成。
Primate fossil assemblages often have metacarpals and phalanges from which functional/behavioral interpretations may be inferred. For example, intrinsic hand proportions can indicate hand function and substrate use. But, estimates of intrinsic hand proportions from unassociated hand elements can be imperfect due to digit misattribution. Although isolated metacarpals can be identified to a specific digit, phalanges are difficult to assign to a specific ray. We used a resampling approach to evaluate how estimates of intrinsic hand proportions are affected by such uncertainty. First, the phalangeal index-intermediate phalanx length plus proximal phalanx length divided by metacarpal length-for the third digit was calculated for associated specimens of terrestrial, semiterrestrial, and arboreal taxa. We then used resampling procedures to generate distributions of "composite digits" based on resampled ratios in which phalanges from the second, fourth, and fifth rays, and from different individuals, were chosen randomly. Results confirm that the phalangeal index for associated third digits significantly discriminates groups. We also found that resampled ratios had significantly lower means, indicating that using composite digits is prone to systematic underestimation. Resampled ratios also generated distributions with greater variance around the means that obscured distinctions between groups, although significant differences between the most arboreal and terrestrial taxa are maintained. We conclude that using unassociated phalanges to calculate a phalangeal index is prone to sampling bias. Nevertheless, a resampling approach has the potential to inform estimates of hand proportions for fossil taxa, provided that the comparative sample is constrained to mimic the fossil composition.