Doctoral Dissertation Improvement: Functional Analysis of Primate Semicircular Canal Morphology in Relation to Locomotor Head Accelerations

从化石中重建运动模式对于理解灵长类动物的起源和各种分支的重要转变至关重要。 最近的研究表明，内耳半规管的结构提供了有关运动的证据。 运河感觉旋转头部加速度和驱动反射基本的正常运动。 骨道曲率半径可以在骨标本和化石中测量，预测骨道敏感性。 在现存的灵长类动物和灭绝的灵长类动物中，运河形态的变化被归因于运动行为的种间差异。 然而，运动选择运河形态的方式存在争议。 虽然有些人认为，大的敏感运河是自适应检测缓慢的头部加速度（“慢敏感假设”），其他人认为，大的敏感运河是自适应检测快速头部加速度（“快敏感假设”）。 试图重建运动偏好的古生物学家从这两种假设中推断出了相反的结论，即生活中头部运动的整体敏捷性和方向性。 替代方案无法测试，因为没有关于灵长类动物旋转头部加速度的实际数据。 要完善拟议的运河形态和运动功能之间的联系，并解决相互矛盾的功能解释，本研究将探讨旋转头加速度在strepsirhine灵长类动物表现出不同的运动行为。 运动过程中的头部加速度将使用三维运动学分析来表征。 头颅CT扫描将用于测量椎管曲率半径，并模拟椎管对不同方向旋转的敏感性。 运动头加速度的直接测量，然后将进行比较，以测试预测的慢敏感和快敏感hypothes.semicircular运河形态的敏感性形态的决定因素可能提供线索的运动在灭绝的类群是分开的，不同的信息提供的postcranial仍然。 了解行为如何选择运河形态是至关重要的，使这种性质的准确推断。 该项目将首次表征灵长类动物头部运动加速度。 这些数据将被用来评估竞争的假设半规管形态和运动头加速度之间的自适应联系。 它将促进对灭绝灵长类动物运动适应的理解，并将有助于确定基于化石管道的运动重建的限制。此外，使用strepsirhines可能有利于推断与灵长类动物起源相关的运动适应和进化转变。

Reconstructing locomotor patterns from fossils is crucial for understanding the origins of primates and important transitions in various clades. Recent studies suggest that the structure of the semicircular canals of the inner ear provides evidence about locomotion. The canals sense rotational head accelerations and drive reflexes essential for normal movement. Canal radius of curvature, which can be measured in osteologic specimens and fossils, predicts canal sensitivity. Variation in canal morphology in living and, by inference, extinct primates has been attributed to interspecific differences in locomotor behavior. However, the manner in which movement selects for canal morphology is debated. While some argue that large sensitive canals are adaptive for detecting slow head accelerations (the "slow-sensitive hypothesis"), others contend that large sensitive canals are adaptive for detecting fast head accelerations (the "fast-sensitive hypothesis"). Paleontologists seeking to reconstruct locomotor preferences have extrapolated from both hypotheses to arrive at opposing conclusions about overall agility and patterns of directional head movement in life. Alternative scenarios cannot be tested because there are no actual data about rotational head accelerations in primates. To refine proposed links between canal morphology and locomotor function, and to resolve conflicting functional interpretations, this study will examine rotational head accelerations in strepsirhine primates exhibiting diverse locomotor behaviors. Head accelerations during locomotion will be characterized using 3-dimensional kinematic analyses. Cranial CT scans will be used to measure canal radii of curvature and to model canal sensitivity to rotations in different directions. Direct measurements of locomotor head accelerations will then be compared to morphologic determinants of sensitivity to test predictions of the slow-sensitive and fast-sensitive hypotheses.Semicircular canal morphology may offer clues about locomotion in extinct taxa that are separate and distinct from the information provided by postcranial remains. Understanding how behavior selects for canal morphology is critical for making accurate inferences of this nature. This project will supply the first characterization of locomotor head accelerations in primates. These data will be used to evaluate competing hypotheses about the adaptive link between semicircular canal morphology and locomotor head accelerations. It will advance understanding of locomotor adaptation in extinct primates and will help to define the limits of fossil-canal-based locomotor reconstruction. Moreover, the use of strepsirhines may advantage inferences about the locomotor adaptations and evolutionary shifts associated with primate origins.