It always has been official - where permitted by the army list - such as Spartan Sp(O) supporting Sp(S).
Not so in the Carthaginian list sorry.
sp(S) are tough troops against anything that takes the -1 for them having a 2nd rank (which is mainly other spear!!) - but still a problem vs anything that quick kills them - mainly because 2 ME's is too much to lose so easily.