The hyoid contributes to a range of functional behaviors such as breathing, swallowing, and vocalization. Among nonhuman primates, hyoid morphology and position show taxonomic differences. For example, cercopithecoid hyoids are more anatomically constrained than hominoid hyoids, which may influence their morphology. While most of the existing literature on the hyoid in nonhuman primates compares morphological differences among species, studies of intraspecific hyoid morphological variation are scarce. This study used a geometric morphometric approach to examine the effects of age and sex on hyoid morphology in Macaca mulatta. The sample comprised 154 skeletal specimens housed at the University of Puerto Rico’s Caribbean Primate Research Center, representing both sexes and an age range of 1–25 years old. I collected three-dimensional landmark coordinate data from the cranium, mandible, and hyoid body of each specimen and tested the effects of age and sex on hyoid morphology through principal components analysis and full factorial analyses. Hyoid shape correlated strongly with age but not sex. Hyoid shape and size correlated strongly with both life history stage and age class. While the hyoid appears to grow within expected body size parameters, hyoid morphology is not fully isometric. Rather, the hyoid exhibits superoinferior lengthening and upward rotation through postnatal ontogeny, with notable upward rotation of the superior surface occurring at 1–4 years of age. As maturational processes such as vocal tract lengthening impose age-linked constraints on vocal behavior, these findings suggest that the hyoid grows in relation to surrounding vocal tract anatomy, and that hyoid shape may contribute to structural support for age-linked vocalization.

中文翻译：

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猕猴舌骨体的生长和两性异形

舌骨有助于一系列功能行为，如呼吸、吞咽和发声。在非人类灵长类动物中，舌骨形态和位置显示分类差异。例如，cercopithecoid 舌骨比人科舌骨在解剖学上更受限制，这可能会影响它们的形态。虽然大多数关于非人类灵长类动物舌骨的现有文献比较了物种之间的形态差异，但对种内舌骨形态变异的研究很少。本研究使用几何形态测量方法来检查年龄和性别对猕猴舌骨形态的影响。样本包括位于波多黎各大学加勒比灵长类动物研究中心的 154 个骨骼标本，代表两性和 1-25 岁的年龄范围。我从每个标本的颅骨、下颌骨和舌骨体中收集了三维地标坐标数据，并通过主成分分析和全因子分析测试了年龄和性别对舌骨形态的影响。舌骨形状与年龄密切相关，但与性别无关。舌骨形状和大小与生活史阶段和年​​龄等级密切相关。虽然舌骨似乎在预期的体型参数内生长，但舌骨形态并不是完全等距的。相反，舌骨通过出生后的个体发育表现出上下延长和向上旋转，上表面的显着向上旋转发生在 1-4 岁时。由于声道延长等成熟过程对发声行为施加了与年龄相关的限制，