We show that spacelike
S-Willmore surfaces are the only spacelike Willmore surfaces with a duality in
Lorentzian space forms. We obtain a classification of S-Willmore spheres in
Lorentzian conformal space forms. Such a sphere must be congruent to either a
complete spacelike stationary (H= 0) surface in R1n; a super-Willmore sphere
in S2m+2; or a polar transform of a (j − 1)-isotropic complete spacelike
stationary (H= 0) surface in R12j+2. We also show that all Willmore
spheres in Q14 are conformal to a complete spacelike stationary surface in
R14.