Jasinoski Sandra C, Rayfield Emily J, Chinsamy Anusuya
Department of Earth Sciences, University of Bristol, Wills Memorial Building, Bristol BS8 1RJ, UK.
J Morphol. 2010 Jun;271(6):705-28. doi: 10.1002/jmor.10828.
Cranial suture morphology of Lystrosaurus and the generalized dicynodont Oudenodon was investigated to determine the strain environment during mastication, which in turn may indicate a difference in cranial function between the two taxa. Finite element (FE) analysis indicated that less strain accumulated in the cranium of Lystrosaurus during orthal bite simulations than in Oudenodon. Despite the overall difference in strain magnitude, moderate to high FE-predicted strain accumulated in similar areas of the cranium of both taxa. The suture morphology in these cranial regions of Lystrosaurus and Oudenodon was investigated further by examination of histological sections and supplemented by observations of serial sections and computed tomography (CT) scans. The predominant type of strain from selected blocks of finite elements that contain sutures was determined, enabling comparison of suture morphology to strain type. Drawing from strain-suture correlations established in extant taxa, the observed patterns of sutural morphology for both dicynodonts were used to deduce cranial function. The moderate to high compressive and tensile strain experienced by the infraorbital bar, zygomatic arch, and postorbital bar of Oudenodon and Lystrosaurus may have been decreased by small adjustive movements at the scarf sutures in those regions. Disparities in cranial suture morphology between the two taxa may reflect differences in cranial function. For instance, the tongue and groove morphology of the postorbital-parietal suture in Oudenodon could have withstood the higher FE-predicted tensile strain in the posterior skull roof. The scarf premaxilla-nasal suture of Lystrosaurus provided an additional region of sutural mobility in the anterior surface of the snout, suggesting that Lystrosaurus may have employed a different biting regime than Oudenodon. The morphology of several sutures sampled in this study correlated with the FE-predicted strain, although other cranial functional hypotheses remain to be tested.
研究了水龙兽和广义二齿兽类欧登多兽的颅缝形态，以确定咀嚼过程中的应变环境，这反过来可能表明这两个类群在颅骨功能上的差异。有限元（FE）分析表明，在垂直咬合模拟中，水龙兽颅骨中积累的应变比欧登多兽少。尽管应变大小存在总体差异，但在这两个类群的颅骨相似区域中，有限元预测的应变积累为中等到高。通过检查组织学切片，并辅以连续切片观察和计算机断层扫描（CT）扫描，进一步研究了水龙兽和欧登多兽这些颅骨区域的缝形态。确定了包含缝的有限元选定块中的主要应变类型，从而能够将缝形态与应变类型进行比较。根据现存类群中建立的应变-缝相关性，利用观察到的两种二齿兽类的缝形态模式来推断颅骨功能。欧登多兽和水龙兽的眶下棒、颧弓和眶后棒所经历的中等到高的压缩和拉伸应变，可能通过这些区域的嵌合缝处的小调整运动而降低。这两个类群在颅缝形态上的差异可能反映了颅骨功能的差异。例如，欧登多兽眶后-顶骨缝的舌槽形态可能能够承受颅骨后顶更高水平的有限元预测拉伸应变。水龙兽的前上颌-鼻嵌合缝在吻部前表面提供了一个额外的缝活动区域，这表明水龙兽可能采用了与欧登多兽不同的咬嚼方式。尽管其他颅骨功能假说仍有待检验，但本研究中采样的几条缝的形态与有限元预测的应变相关。
