This paper briefly introduces the study history of the Shoutheridia and the significance of Pseudotribos robustus for the study on the evolution of Mesozoic mammal teeth and on the subdivision and correlation of Mesozoic strata in China. The discovery of Pseudotribos robustus not only strongly supports the hypotheses of “tribosphenic molar could have undergone convergent evolution”, but also suggests that the Daohugou Biota is Middle Jurassic in age.