Target 1 "Summoned Skull" or Thunder-Type monster you control; destroy all monsters your opponent controls with DEF less than or equal to the ATK of that monster. You cannot conduct your Battle Phase the turn you activate this card.
If a card says "(name} monster" or "(name") card", then it means all monsters/cards with that name. If it lacks such a word, however, it means a specific name. So, no, it won't work with Toon Summoned Skull (unless the unreleased DNA Surgery or something changes its type to Thunder, of course).