Mechanics of the scarf premaxilla-nasal suture in the snout of Lystrosaurus
Mechanics of the scarf premaxilla-nasal suture in the snout of Lystrosaurus
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DOI：
10.1080/02724634.2010.483556
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发表时间：
2010-01-01
影响因子：
1.4
通讯作者：
Chinsamy, Anusuya
中科院分区：
文献类型：
--
作者：
Jasinoski, Sandra C.;Rayfield, Emily J.;Chinsamy, Anusuya
颅缝可以防止在加载过程中高应变在周围坚硬的颅骨中积累（Herring和Ochareon，2005）。胶原纤维的网络赋予缝线顺应性材料特性，允许通过变形吸收能量，从而降低局部骨应变（Jaslow，1990; Margulies和Thibault，2000; Raffaly等人，2003年）。在咀嚼过程中，颅缝可以消散肌肉收缩和咬合产生的力（例如，Raffaline和Herring，1999; Herring和Teng，2000）。颅缝的形态可以反映它们所经历的主要类型的应变（Herring和Mucci，1991; Raffeine和Herring，1999; Markey等人，2006年）。指状交叉缝合出现在压迫区域，而张力区域倾向于有对接端缝合（Herring和Mucci，1991; Herring和Teng，2000）。围巾或重叠缝线可以承受两种类型的应变（Jenkins等人，2002; Markey等人，2006年）。水龙兽是一种独特的双齿兽，有着腹侧延长的吻部和前后缩短的头骨（King，1990），并且是唯一已知跨越二叠纪-三叠纪灭绝界限的双齿兽属（Smith和博塔，2005）。水龙兽吻部的前颌骨-鼻缝具有独特的围巾状形态（King和Cluver，1991; Jasinoski等人，2010;图1A）。这与Oudenodon的叉指状前颌骨-鼻缝形成鲜明对比（Jasinoski等人，2010）和其他双齿龙。这种形态上的差异表明，缝在水龙龙的吻部中起着不同的作用。有人假设水龙龙的前颚-鼻缝可以容纳一些微小的运动，因此在强力的咬或掘活动中充当“减震器”（King和Cluver，1991）。一个基于内收肌肌肉组织的机械优势的更近期的假设表明，水龙兽在进食期间施加了动态咬合（Jasinoski等人，2009），从而支持前颌骨-鼻缝的应变调节假说（Jasinoski等人，先前的水龙龙的颅骨（没有下颌骨的颅骨）的有限元（FE）模型记录了在静态正上颌骨咬合期间固定和融合的前上颌骨-鼻缝区域内的适度压缩应变（Jasinoski等人，2010年）。其他有限元研究表明，将颅缝引入颅骨的有限元模型可以改变颅骨上的应变大小和模式（Rayfield，2004，2005; Kupczik等人，2007; Moazen等人，2009年）。本研究测试这种独特的围巾接触如何容纳和重新分配的应力和应变在静态orthal喙咬相比，融合颅模型。将颅骨的骨学特征与应力和应变重新分布的区域进行比较，可以确定
Cranial sutures can prevent high strain from accumulating in the surrounding stiff cranial bones during loading (Herring and Ochareon, 2005). A network of collagen fibers imparts compliant material properties to sutures, allowing absorption of energy through deformation, thereby decreasing local bone strain (Jaslow, 1990; Margulies and Thibault, 2000; Rafferty et al., 2003). During mastication, cranial sutures can dissipate forces generated by muscle contraction and occlusion (eg, Rafferty and Herring, 1999; Herring and Teng, 2000). The morphology of cranial sutures can reflect the predominant type of strain they experience (Herring and Mucci, 1991; Rafferty and Herring, 1999; Markey et al., 2006). Interdigitated sutures occur in regions of compression, whereas areas of tension tend to have butt-ended sutures (Herring and Mucci, 1991; Herring and Teng, 2000). Scarf or overlapping sutures can withstand both types of strain (Jenkins et al., 2002; Markey et al., 2006). Lystrosaurus was a distinctive dicynodont with a ventrally elongated snout and anteroposteriorly shortened skull (King, 1990), and is the only dicynodont genus known to cross the Permo-Triassic extinction boundary (Smith and Botha, 2005). The premaxilla-nasal suture in the snout of Lystrosaurus has a distinctive scarf morphology (King and Cluver, 1991; Jasinoski et al., 2010; Fig. 1A). This is in stark contrast to the interdigitated premaxilla-nasal suture of Oudenodon (Jasinoski et al., 2010) and possibly other dicynodonts. This difference in morphology suggests that the suture served a different function in the snout of Lystrosaurus. It has been hypothesized that the premaxilla-nasal suture of Lystrosaurus accommodated some micro-movement and thus acted as a ‘shock-absorber’during forceful biting or grubbing activities (King and Cluver, 1991). A more recent hypothesis based on the mechanical advantage of the adductor musculature suggested that Lystrosaurus exerted a dynamic snapping bite during feeding (Jasinoski et al., 2009), thus supporting the strain accommodation hypothesis for the premaxilla-nasal suture (Jasinoski et al., 2010).A previous finite element (FE) model of the cranium (skull without the mandible) of Lystrosaurus documented moderate compressive strain within the region of an immobilized and fused premaxilla-nasal suture during a static orthal maxilla bite (Jasinoski et al., 2010). Other FE-studies have shown that the introduction of cranial sutures into a finite element model of the cranium can change the magnitude and the patterns of strain across the cranium (Rayfield, 2004, 2005; Kupczik et al., 2007; Moazen et al., 2009). The present study tests how this distinctive scarf contact accommodates and redistributes stress and strain during a static orthal beak bite in comparison to a fused cranial model. Comparison of the cranial osteological features with the regions of redistributed stress and strain can determine if