The teeth of all vertebrates predominantly comprise the same materials, but their lifespans vary widely: in stark contrast to mammals, shark teeth are functional only for weeks, rather than decades, making lifelong durability largely irrelevant. However, their diets are diverse and often mechanically demanding, and as such, their teeth should maintain a functional morphology, even in the face of extremely high and potentially damaging contact stresses. Here, we reconcile the dilemma between the need for an operative tooth geometry and the unavoidable damage inherent to feeding on hard foods, demonstrating that the tooth cusps of Port Jackson sharks, hard-shelled prey specialists, possess unusual microarchitecture that controls tooth erosion in a way that maintains functional cusp shape. The graded architecture in the enameloid provokes a location-specific damage response, combining chipping of outer enameloid and smooth wear of inner enameloid to preserve an efficient shape for grasping hard prey. Our discovery provides experimental support for the dominant theory that multi-layered tooth enameloid facilitated evolutionary diversification of shark ecologies.

所有脊椎动物的牙齿主要由相同的材料组成，但它们的寿命差异很大：与哺乳动物形成鲜明对比的是，鲨鱼的牙齿仅可使用数周而不是数十年，因此终身寿命基本不相关。但是，它们的饮食各不相同，并且通常对机械要求很高，因此，即使面对极高的潜在潜在接触压力，它们的牙齿也应保持功能形态。在这里，我们调和了需要有效操作牙齿的几何形状与以硬食为食所不可避免不可避免的损害之间的两难选择，这表明硬壳猎物专家波特杰克鲨鱼的牙尖具有非常规的微结构，可以控制牙齿的腐蚀。保持功能性尖端形状的方式。雌雄同体中的渐变结构引发了特定位置的损坏响应，将外部雌雄同体的碎裂和内部雌雄同体的光滑磨损结合在一起，从而保留了有效的形状以抓取坚硬的猎物。我们的发现为占主导地位的理论提供了实验支持，该理论认为多层牙齿同名生物促进了鲨鱼生态学的进化多样化。