New information on the dentition and tooth replacement of Nothosaurus (Reptilia: Sauropterygia)

Dental morphology and tooth replacement of Nothosaurus are described and discussed in detail based on two well-preserved specimens of N. rostellatus and a skull of Nothosaurus sp. from the Middle Triassic Guanling Formation in Guizhou, South China. This study indicates that tooth replacement is sequentially alternative and asynchronous in the premaxilla, but with a wave-like pattern and synchronous in the maxilla in Nothosaurus. The replacement process is from front to back in the premaxilla, and three stages of tooth replace succession can be recognized. The incongruent tooth replacement rhythms in the premaxilla and maxilla may be related to different tooth functions.