The paper presents two new kinematic schemes of articulated planar mechanisms used as legs in a quadruped mobile robot. These mechanisms consist of 5 mobile kinematic elements when it is compared to the Jansen mechanism which is made of 7 elements. The four leg mechanisms of the quadruped robot are driven by a single electric motor by means of spur gears. The structure of the mechanism is consisting of kinematic chains with four articulated triadic or tetradic elements. For each of the proposed kinematic schemes, several geometrical options regarding the position of the articulations and the fulcrum have been considered. The mobility of each kinematic scheme is assessed and a geometrical synthesis method for generating the reciprocating coupler curve of the fulcrum is given.