Dissertation Research: Evolution and Functional Morphology of Incisors in Wood-cutting Castorids

啮齿动物比任何其他哺乳动物种类都更多样、更丰富。虽然他们的成功与上下一对不断增长的门牙有关，但人们对门牙形状和行为之间的进化关系知之甚少(例如。在这些动物中)。这项研究将考察化石和活海狸的门牙形状与木刻进化的关系。人们对木头切割特别感兴趣，因为木头非常坚硬，经常砍伐木头的啮齿类动物应该展示专门用于这种行为的门牙。这两种活着的海狸在外观上很相似，而且砍伐木材的范围很广。然而，化石海狸是一个更加多样化的群体。例如，它们的大小从松鼠到黑熊都有。一些人用他们的门牙来挖掘。他们还拥有各种各样的门牙形状。事实上，已知的一种会砍柴的海狸的门牙与活着的海狸的门牙形状不同。这些形状不同的门牙对于木刻的进化有什么行为和进化意义？这个问题将通过重建海狸之间的进化关系，研究现存啮齿动物门牙形状、行为和身体大小之间的关系来回答。PI还将检查牙齿磨损的微观特征，因为这些特征可能有助于确定啮齿动物门牙的功能。这项研究将有助于我们进一步理解动物形态与环境之间的进化关系。海狸在这方面特别感兴趣，因为它们对生态系统的结构和可能的进化有异常大的影响。

Rodents are more diverse and abundant than any other mammal group. Although their success has been linked to an upper and lower pair of ever-growing incisors, little is known about the evolutionary relationship between incisor shape and behavior (ex. diet) in these animals. This study will examine incisor shape in fossil and living beavers with respect to the evolution of wood-cutting. Wood-cutting is of particular interest because wood is extremely tough and it might be expected that rodents that frequently cut wood should exhibit incisors specialized for that behavior. Both living species of beaver are similar in appearance and cut wood extensively. Fossil beavers, however, are a more diverse group. For example, they ranged in size from squirrel to black-bear size. Some used their incisor for digging. They also possessed a diversity of incisor shapes. In fact, one beaver that is known to have cut wood has incisors that differ in shape from those of the living beaver. What is the behavioral and evolutionary significance of these differently shaped incisors with respect to the evolution of wood-cutting? This question will be answered by reconstructing the evolutionary relationships among beavers, studying the relationship between incisor-shape, behavior and body-size in living rodents. The PI will also examine microscopic tooth-wear features as these might help determine how rodents incisors function. This research will serve to further our understanding of the evolutionary relationship between animal form and environment. Beavers are of particular interest in this regard because they have an unusually large impact on the structure and possibly the evolution of ecosystems.