剑齿食肉动物在长时间犬齿喷出期间弯曲性能的变化:Smilodon fatalis 的案例研究

Z. Jack Tseng
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引用次数: 0

摘要

剑齿食肉动物的犬齿是已知最特化的牙齿结构之一。关于肥大犬齿的功能,有各种假设,包括展示和同类互动、软性食物加工,以及主动捕获猎物。最近对头骨特征的发育时间的研究表明,成年犬齿可能需要数年才能完全萌出,但目前的论述中还没有提及萌出时间过长对推断犬齿功能形态的影响,也没有对其进行量化。在此,我评估了关于长尾鼬爆发期间成年犬齿弯曲强度和刚度的假设。通过标本模型生成了三颗成年犬齿的模拟喷发序列,以评估横截面几何形状的移动特性,并使用有限元分析估算了横向载荷作用下的弯曲强度和刚度。与梁理论的预期一致,S. fatalis 犬齿横截面几何形状经过优化,随着喷发高度的增加,弯曲强度也会增加。然而,犬齿横截面几何形状在萌发过程中的变化会加剧而不是减小横向挠度。据推测,上颌相邻感觉结构对最大牙根长度的空间限制以及最近发现的普遍幂律限制了犬齿前后长度的增长能力,从而限制了萌出过程中弯曲刚度的维持。相反,在50%的成人犬齿萌出期,乳牙和成人犬齿的共同存在有效地增加了犬齿的内外侧宽度,使弯曲强度和刚度估计值更接近理论上的最佳值。在其他剑齿象中,落叶犬齿的长期保持同样表明,双犬齿对接是一种趋同进化策略,可以最大限度地提高弯曲强度和刚度。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Bending performance changes during prolonged canine eruption in saber‐toothed carnivores: A case study of Smilodon fatalis
The canine of saber‐toothed predators represents one of the most specialized dental structures known. Hypotheses about the function of hypertrophied canines range from display and conspecific interaction, soft food processing, to active prey acquisition. Recent research on the ontogenetic timing of skull traits indicates the adult canine can take years to fully erupt, but the consequences of prolonged eruption on inferences of canine functional morphology are missing from current discourse and have not been quantified. Here I evaluate hypotheses about adult canine bending strength and stiffness, respectively, during eruption in the felid Smilodon fatalis. Simulated eruption sequences of three adult canines were generated from specimen models to assess shifting cross‐sectional geometry properties, and bending strength and stiffness under laterally directed loads were estimated using finite element analysis. Consistent with beam theory expectations, S. fatalis canine cross‐sectional geometry is optimized for increased bending strength with increased erupted height. However, canine cross‐sectional geometry changes through eruption exaggerate rather than minimize lateral deflection. Spatial constraint for maximum root length from adjacent sensory structures in the maxilla and the recently identified universal power law are hypothesized to limit the growth capacity of canine anteroposterior length and, consequently, maintenance of bending stiffness through eruption. Instead, the joint presence of the deciduous and adult canines for >50% of the adult canine eruption period effectively increases canine mediolateral width and brings bending strength and stiffness estimates closer to theoretical optima. Similarly prolonged retention of deciduous canines in other sabertooths suggests dual‐canine buttressing is a convergently evolved strategy to maximize bending strength and stiffness.
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