abstractThe close relationships of pinnipeds to other carnivorans were studied based on morphological characteristics of the bony tentorium (BT) and bony falx (BF) of carnivorans. It appears to be an important characteristic of the Carnivora that the clear BT is present in almost all species including pinnipeds. The BF is present in all species of pinnipeds, and only in the genusUrsusamong fissipeds observed.The parietal bone of all otariids and odobenids observed shows an extremely characteristic form as compared with other carnivorans. The sagittal and squa‐mous borders of the parietal bone of these groups are bridged by a thin bony plate which forms large portions of the BT and BF. In phocids, the aspects of the BT and BF vary among species, but are apparently distinct from those of otariids and odobenids.The BT of carnivorans can be divided into four types which appear to be useful for classification of the Carnivora. On the basis of the BT and BF form, the Otariidae and Odobenidae appear to have a specific sister relationship to the Ursidae, while the Phocidae appears to have dose affinities to the Mustelidae. Morphological differences of the BT and BF among pinnipeds strongly support the diphyletic origin of pinniped