Abstract: The diagnostic characters of the two species in Sinoadapis described previously in Lufeng specimens have been observed to be continuous through transitional phenotypes and the combinations of characters of the two species exist in some specimens. These characters are hereby not of taxonomic value but variations within a single species. Therefore, Sinoadapis shihuibaensis is considered to be a synonym of Sinoadapis carnosus and should be sunk. Sinoadapis in Lufeng is treated as a genus of single species.
The diagnostic characters which distinguish Sivaladapis from Indraloris from the Siwaliks of India and Pakistan art analogous to those for distinguishing the two “species” of Sinoadapis. It is believed that the “gap” between the two genera would be filled by specimens which have not been discovered yet. It is probable that they may be a synonymous genus or even species.
The distributions of each dimension of upper and lower canines in Sinoudapis are sexually non-overlapping with the exception of upper canine breadth probably due to the small sample size. Consequently, the canine specimens are easily sexed. As a measure of canine size dimorphism, the male/female ratio for a single dimension is determined to be 1.2.
Unlike the canines, the distributions of each dimension of the lower 4th premolars are sexually overlapping or sexually non-discriminating, Nevertheless, the bi-dimensional distribution of length and breadth of the teeth reveals to some extent the existence of two clusters with few intermediates in the area of both means in sexually pooled sample. The concentrations represent the male and female averages of the measurements concerned respectively. The size dimorphism of the lower 4th premolars estimated by this way bas a ratio of 1.08. If this ratio is representative of the extent of generalized body dimorphism in one dimension, the male/female ratio of body weight might be estimated to be 1.26, or 8kg for male average and 6.4 kg for female average.

Key words: Sinoadapis carnosus; Sinoadapis shihuibaensis; Sexual dimorphism; Sexual discriminating