Mandibular mobility accompanying gape change in Northern and Antarctic minke whales was investigated by manipulating jaws of carcasses, recording jaw movements via digital instruments (inclinometers, accelerometers, and goniometers), and examining osteological and soft tissue movements via computed tomography (CT)‐scans. We investigated longitudinal (α) rotation of the mandible and mediolateral displacement at the symphysis (Ω1) and temporomandibular joint (Ω2) as the mouth opened (Δ). Results indicated three phases of jaw opening. In the first phase, as gape increased from zero to 8°, there was slight (<1°) α and Ω rotation. As gape increased between 20 and 30°, the mandibles rotated slightly laterally (Mean 3°), the posterior condyles were slightly medially displaced (Mean 4°), and the anterior ends at the symphysis were laterally displaced (Mean 3°). In the third phase of jaw opening, from 30° to full (≥90°) gape, these motions reversed: mandibles rotated medially (Mean 29°), condyles were laterally displaced (Mean 14°), and symphyseal ends were medially displaced (Mean 1°). Movements were observed during jaw manipulation and analyzed with CT‐images that confirmed quantitative inclinometer/accelerometer data, including the unstable intermediate (Phase 2) position. Together these shifting movements maintain a constant distance for adductor muscles stretched between the skull's temporal fossa and mandible's coronoid process. Mandibular rotation enlarges the buccal cavity's volume as much as 36%, likely to improve prey capture in rorqual lunge feeding; it may strengthen and stabilize jaw opening or closure, perhaps via a simple locking or unlocking mechanism. Rotated lips may brace baleen racks during filtration. Mandibular movements may serve a proprioceptive mechanosensory function, perhaps via the symphyseal organ, to guide prey engulfment and water expulsion for filtration.

中文翻译：

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小须鲸颞下颌关节的多轴运动

通过操纵尸体的下颚，通过数字仪器（倾角仪、加速度计和测角仪）记录下颌运动，并通过计算机断层扫描 (CT) 扫描检查骨骼和软组织运动，研究了伴随着北南极和南极小须鲸张嘴变化的下颌活动性。我们研究了当嘴巴张开 (Δ) 时下颌骨的纵向 (α) 旋转和联合 (Ω1) 和颞下颌关节 (Ω2) 处的中外侧位移。结果表明下颌张开的三个阶段。在第一阶段，随着间隙从 0 增加到 8°，α 和 Ω 有轻微的 (<1°) 旋转。随着间隙在 20° 和 30° 之间增加，下颌骨轻微横向旋转（平均 3°），后髁略微向内移位（平均 4°），并且联合处的前端横向移位（平均3°）。在下颌张开的第三阶段，从 30° 到完全（≥90°）张开，这些运动逆转：下颌骨向内旋转（平均 29°），髁突向外侧移位（平均 14°），并且联合末端向内侧移位平均 1°）。在下颌操作过程中观察运动，并使用 CT 图像进行分析，确认定量倾角计/加速度计数据，包括不稳定的中间（第 2 阶段）位置。这些移位运动共同为在颅骨颞窝和下颌骨冠突之间伸展的内收肌保持恒定距离。下颌旋转使颊腔的体积扩大了 36%，可能会提高 rorqual 弓步进食中的猎物捕获率；它可以加强和稳定下巴的张开或闭合，也许通过一个简单的锁定或解锁机制。在过滤过程中，旋转的唇缘可能会支撑鲸须架。下颌运动可能具有本体感觉的机械感觉功能，可能通过交感器官引导猎物吞食和排出水以进行过滤。