Evolutionary and Biological Implications of Dental Mesial Drift in Rodents: The Case of the Ctenodactylidae (Rodentia, Mammalia)
Evolutionary and Biological Implications of Dental Mesial Drift in Rodents: The Case of the Ctenodactylidae (Rodentia, Mammalia)
复制标题
啮齿类动物牙齿近中漂移的进化和生物学意义：栉指动物科（啮齿目、哺乳动物）案例
作者：
Helder Gomes Rodrigues;F. Solé;C. Charles;P. Tafforeau;M. Vianey;L. Viriot
牙齿特征对于重建哺乳动物的进化历史非常重要，因为牙齿代表了化石物种中最丰富的材料。然而，牙齿更新的特点，目前很少使用，可能是因为牙齿公式往往没有正确地建立，而他们可能是高度关注的进化和发展问题。最古老的啮齿动物家族之一，Cteenacytylidae，有趣的是有长期争议的牙齿公式。在这里，我们调查了70个头骨之间的所有现存的cteacetiactylid属（cteacetiactylus，Felovia，Massoutiera和Pectinator）通过使用X射线常规和同步辐射显微断层扫描，以解决和讨论这些牙科问题。我们的研究清楚地表明，Massoutiera、Felovia和Ctenodactylus与Pectinator的不同之处不仅在于更衍生的齿系，而且还在于更衍生的喷发序列。除臼齿外，他们的齿列只包括第四乳前臼齿，而不再有恒牙前臼齿，与Pectinator相反。此外，我们发现这些前磨牙在成年期丢失，因为磨牙的近中漂移。近中移动是一个引人注目的机制，涉及骨重建和牙齿吸收允许的牙齿迁移。迄今为止，这种牙科创新在啮齿动物中知之甚少，因为它只是第二次报告。有趣的是，我们注意到啮齿类动物的牙齿漂移总是与高冠牙齿有关，有利于磨牙尺寸的扩大。因此，它可以代表另一种适应，以承受高磨损，因为这些啮齿动物居住在沙漠环境中，灰尘丰富。从进化、生物学和正畸学的角度来看，对啮齿类动物近中偏移进行更准确的研究将是非常有希望的。
Dental characters are importantly used for reconstructing the evolutionary history of mammals, because teeth represent the most abundant material available for the fossil species. However, the characteristics of dental renewal are presently poorly used, probably because dental formulae are frequently not properly established, whereas they could be of high interest for evolutionary and developmental issues. One of the oldest rodent families, the Ctenodactylidae, is intriguing in having longstanding disputed dental formulae. Here, we investigated 70 skulls among all extant ctenodactylid genera (Ctenodactylus, Felovia, Massoutiera and Pectinator) by using X-ray conventional and synchrotron microtomography in order to solve and discuss these dental issues. Our study clearly indicates that Massoutiera, Felovia and Ctenodactylus differ from Pectinator not only by a more derived dentition, but also by a more derived eruptive sequence. In addition to molars, their dentition only includes the fourth deciduous premolars, and no longer bears permanent premolars, conversely to Pectinator. Moreover, we found that these premolars are lost during adulthood, because of mesial drift of molars. Mesial drift is a striking mechanism involving migration of teeth allowed by both bone remodeling and dental resorption. This dental innovation is to date poorly known in rodents, since it is only the second report described. Interestingly, we noted that dental drift in rodents is always associated with high-crowned teeth favoring molar size enlargement. It can thus represent another adaptation to withstand high wear, inasmuch as these rodents inhabit desert environments where dust is abundant. A more accurate study of mesial drift in rodents would be very promising from evolutionary, biological and orthodontic points of view.