RESUMEN
Based on the anatomical study of kidney in mammals of 27 families and 163 species, the authors discovered Anoa depressicornis type kidney, and obtained the evidence of morphological transition between Ox-type kidney and Pig-type kidney. After observing the renal papillary structure of Budorcas taxicolor, the evidence of fact and theoretical bases of the biological view was proved that the general papillae are developed from the multi-papillae kidney. The author advanced a new type of leaf-shaped multipapillae kidney. The authors suggest to classify the mammalian kidneys principally into 2 groups, i. e, simple and composite kidney, and subdivide them into 4 types, i. e, multipapillae and concentrated papillae for simple kidney and leaf-shaped multipapillae and ball-shaped mono-papillae for composite kidney. In contrast to the previous classification, the 2-group 4-type classification recommended here with its solid anatomical foundation is conformable with the viewpoint of biology, and is more practical and integrated.