Department of Biological Sciences, North Carolina State University, Raleigh, North Carolina, USA.
Pathology, Anatomy, and Laboratory Medicine Department, West Virginia University School of Medicine, Morgantown, West Virginia, USA.
J Morphol. 2021 Oct;282(10):1499-1513. doi: 10.1002/jmor.21400. Epub 2021 Aug 6.
In carnivorans, bite force is a critical and ecologically informative variable that has been correlated with multiple morphological, behavioral, and environmental attributes. Whereas in vivo measures of biting performance are difficult to obtain in many taxa-and impossible in extinct species-numerous osteological proxies exist for estimating masticatory muscle size and force. These proxies include both volumetric approximations of muscle dimensions and direct measurements of muscular attachment sites. In this study, we compare three cranial osteological techniques for estimating muscle size (including 2D-photographic and 3D-surface data approaches) against dissection-derived muscle weights and physiological cross-sectional area (PCSA) within the jaw adductor musculature of 40 carnivoran taxa spanning eight families, four orders of magnitude in body size, and the full dietary spectrum of the order. Our results indicate that 3D-approaches provide more accurate estimates of muscle size than do surfaces measured from 2D-lateral photographs. However, estimates of a muscle's maximum cross-sectional area are more closely correlated with muscle mass and PCSA than any estimates derived from muscle attachment areas. These findings highlight the importance of accounting for muscle thickness in osteological estimations of the masticatory musculature; as muscles become volumetrically larger, their larger cross-sectional area does not appear to be associated with a proportional increase in the attachment site area. Though volumetric approaches approximate muscle dimensions well across the order as a whole, caution should be exercised when applying any single method as a predictor across diverse phylogenies.
在食肉动物中，咬合力是一个关键的、具有生态信息价值的变量，它与多种形态、行为和环境特征相关。虽然在许多分类群中，活体测量的咬合性能很难获得——在已灭绝的物种中甚至是不可能的——但存在许多骨骼学代理物来估计咀嚼肌的大小和力量。这些代理物包括肌肉尺寸的体积近似和肌肉附着点的直接测量。在这项研究中，我们比较了三种颅骨骨骼学技术，用于估计肌肉大小（包括 2D 摄影和 3D 表面数据方法），并与 40 种食肉动物分类群的下颌骨内收肌的肌肉重量和生理横截面积（PCSA）进行了比较，这些分类群跨越了八个科，体型大小跨越了四个数量级，并且涵盖了该目的完整饮食谱。我们的结果表明，3D 方法比从 2D 侧位照片测量的表面提供更准确的肌肉大小估计。然而，与任何源自肌肉附着区域的估计相比，肌肉的最大横截面积的估计与肌肉质量和 PCSA 的相关性更高。这些发现强调了在骨骼学上估计咀嚼肌时考虑肌肉厚度的重要性；随着肌肉体积的增加，其更大的横截面积似乎与附着区域面积的比例增加无关。尽管体积方法在整个目范围内很好地近似了肌肉尺寸，但在应用任何单一方法作为跨多种系统发育的预测因子时应谨慎。
