Despite its clear functional role in hock (ankle) plantarflexion, the bovid calcaneus has been understudied with respect to the functional constraints imposed by locomotion in differing habitats, the allometric influence of inter-specific body size differences, and phylogenetic signal. This study uses a comparative sample of extant bovid species to shed light on the evolution of bovid calcaneal morphology. I measured eight linear measurements on 204 calcaneus specimens representing 41 extant bovid species. Using a morphological body size proxy validated against published species-mean body mass estimates, I performed Ordinary Least Squares regression to examine the allometric relationships of each measurement with body size. I classified each bovid species to a preferred habitat type based on published literature, and performed Phylogenetic Generalized Least Squares (PGLS) to test for differences in morphology between bovid taxa with different preferred habitats while considering evolutionary relatedness. I visualized morphological differences between taxa using Principal Components Analysis plotted in a phylomorphospace. Results demonstrate that several measurements of the bovid calcaneus have an allometric relationship to body size. The functional length of the calcaneus scales with negative allometry, which likely maintains a comparable safety factor within the calcaneal tuber at larger body sizes. While open-habitat bovids have relatively shorter calcaneal tubers, this difference is not significant when controlling for the influence of body size and phylogenetic signal using PGLS. Among bovid tribes that have a deep evolutionary history of adaptation to open habitats, Antilopini have relatively longer calcaneal tubers than Alcelaphini or Hippotragini, which may reflect the unique importance of stotting behavior in predator avoidance among antelopins. Overall, the morphology of the bovid calcaneus has been shaped by a complex interaction of phylogenetic and body-size constraints as well as adaptation to modes of predator avoidance mediated by preferred habitat.

中文翻译：

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牛跟骨的形态学：功能、系统发育信号和异速生长

尽管牛科动物跟骨在飞节（脚踝）跖屈中具有明显的功能作用，但在不同栖息地的运动所施加的功能限制、种间体型差异的异速生长影响和系统发育信号方面，牛科动物的跟骨尚未得到充分研究。本研究使用现存牛科动物物种的比较样本来阐明牛科动物跟骨形态的演变。我对代表 41 种现存牛科动物的 204 个跟骨标本进行了八次线性测量。使用根据已发表的物种平均体重估计值验证的形态学体型代理，我进行了普通最小二乘回归来检查每个测量值与体型的异速生长关系。我根据已发表的文献将每种牛科动物分类为首选的栖息地类型，并进行了系统发育广义最小二乘法 (PGLS) 以测试具有不同首选栖息地的牛科动物分类群之间的形态差异，同时考虑到进化相关性。我使用绘制在系统形态空间中的主成分分析来可视化分类群之间的形态差异。结果表明，牛跟骨的几个测量值与体型有异速生长关系。跟骨的功能长度具有负异速生长，这可能在较大的体型下在跟骨结节内保持可比的安全系数。虽然开放栖息地的牛科动物的跟骨块茎相对较短，但在使用 PGLS 控制体型和系统发育信号的影响时，这种差异并不显着。在适应开放栖息地具有深厚进化历史的牛科动物部落中，Antilopini 的跟骨块茎比 Alcelaphini 或 Hippotragini 更长，这可能反映了跺脚行为在羚羊避免捕食者中的独特重要性。总体而言，牛跟骨的形态是由系统发育和体型限制的复杂相互作用以及对由首选栖息地介导的捕食者回避模式的适应所塑造的。