Several tritylodontid taxa have been reported from the Upper Jurassic of the Wucaiwan area in the Junggar Basin of Xinjiang, northwestern China, including Yuanotherium minor. The original study described the partially preserved postcanine teeth in the middle of the left upper maxilla. After detailed re-examination of the specimen and by CT scanning, 3D reconstruction, and scanning electron microscopy observations, we provided a more detailed description of the osteology, neurosensory, and tooth wear pattern for all the bones preserved in this specimen and clarified some characters. Based on new information about the cusp wear pattern, the chewing movement pattern of the dentition and detailed cusp morphology, we discussed the cuspal homology of upper cheek teeth of tritylodontids and postulate a standardized method for cusp identification. We hypothesize that the unique maxilla characteristics furnish the evidence for transitional stages about the evolution of the upper jaw-palate structure in tritylodontids.