Conformal primaries of OSp(8/4,R) and BPS states in AdS(4)

We derive short UIR's of the OSp(8/4, R) superalgebra of 3d N = 8 superconf ormal field theories by the requirement that the highest weight states are annihilated by a subset of the super-Poincare odd generators. We then find a superfield realization of these BPS saturated UIR's as "composite operato rs" of the two basic ultrashort "supersingleton" multiplets. These represen tations are the AdS(4) analogue of BPS states preserving different fraction s of supersymmetry and are therefore suitable to classify perturbative and non-perturbative excitations of M-theory compactifications.