Activate this card by discarding 1 card, then target 1 Dinosaur-Type monster in your Graveyard; Special Summon that target. Its effects are negated. When this card leaves the field, destroy that monster. When that monster is destroyed, destroy this card.
Cards work in a specific way. Since the description doesn't say it gets destroyed when the monster leaves the field, then it won't get destroyed. This is actually intended, since tribute and destroyed are different.