Reptilian Tooth and Jaw Development

爬行动物和哺乳动物有着共同的祖先，可追溯到3亿多年前，但在进化过程中，头骨和牙齿出现了显著的特化。我们的目标是确定在发展过程中这些差异是如何以及何时产生的。例如，大多数爬行动物的头骨比哺乳动物有更多的开口。哺乳动物总是有封闭的上颚，将口腔和鼻腔分开。相比之下，蛇、蜥蜴和鸟类的上颚是开放的，海龟的上颚是原始的，而令人惊讶的是，短吻鳄的上颚和哺乳动物一样是封闭的。在牙列中，牙齿的解剖结构和替换能力也存在显著差异。大多数蛇、蜥蜴和鳄鱼在一生中不断更换牙齿（多齿性），而哺乳动物只能更换一次牙齿。

Reptiles and mammals share a common ancestor dating back more than 300 million years but during evolution significant specializations in the skull and teeth have arisen. Our goal is to determine how and when in development these differences arose. For example, skulls of the majority of reptiles have more openings than mammals. Mammals always have closed palates that separate the oral and nasal cavities. In contrast snakes, lizards and birds have open palates, turtles have a primitive palate and surprisingly alligators have a closed palate like mammals. In the dentition, there are also striking differences in tooth anatomy and replacement capacity. Most snakes, lizards and crocodilians replace their teeth continuously throughout life (polyphyodonty), whereas mammals can only replace their teeth once.