Institute of Biotechnology, Helsinki Institute of Life Science, University of Helsinki, FI-00014, Helsinki, Finland.
Geological Survey of Finland, FI-02150, Espoo, Finland.
Nat Commun. 2021 Oct 14;12(1):6001. doi: 10.1038/s41467-021-26285-w.
Teeth act as tools for acquiring and processing food, thus holding a prominent role in vertebrate evolution. In mammals, dental-dietary adaptations rely on tooth complexity variations controlled by cusp number and pattern. Complexity increase through cusp addition has dominated the diversification of mammals. However, studies of Mammalia alone cannot reveal patterns of tooth complexity conserved throughout vertebrate evolution. Here, we use morphometric and phylogenetic comparative methods across fossil and extant squamates to show they also repeatedly evolved increasingly complex teeth, but with more flexibility than mammals. Since the Late Jurassic, multiple-cusped teeth evolved over 20 times independently from a single-cusped common ancestor. Squamates frequently lost cusps and evolved varied multiple-cusped morphologies at heterogeneous rates. Tooth complexity evolved in correlation with changes in plant consumption, resulting in several major increases in speciation. Complex teeth played a critical role in vertebrate evolution outside Mammalia, with squamates exemplifying a more labile system of dental-dietary evolution.
牙齿作为获取和处理食物的工具，在脊椎动物进化中起着重要作用。在哺乳动物中，牙齿与饮食的适应性依赖于由牙尖数量和模式控制的牙齿复杂性变化。通过增加牙尖的复杂性主导了哺乳动物的多样化。然而，仅对哺乳动物的研究并不能揭示整个脊椎动物进化中牙齿复杂性的模式。在这里，我们使用形态测量学和系统发育比较方法，对化石和现存的有鳞目动物进行研究，结果表明它们也反复进化出越来越复杂的牙齿，但比哺乳动物更具灵活性。自晚侏罗世以来，有超过 20 次从单尖的共同祖先中独立进化出多尖牙齿。有鳞目动物经常失去牙尖，并以不同的速度进化出多样的多尖形态。牙齿的复杂性与植物消耗的变化相关进化，导致了几次主要的物种形成增加。复杂的牙齿在哺乳动物以外的脊椎动物进化中发挥了关键作用，有鳞目动物是牙齿与饮食进化更不稳定系统的典型代表。
