Prowl compares the creature types of the spell with the creature types of the creatures that dealt combat damage to players this turn. For example, this means that normally, if you control Hunting Velociraptor, you can cast Grim Giganotosaurus for its prowl cost only if a Dinosaur dealt combat damage to a player, but if an effect causes the spell to have other creature types, the prowl ability is also satisfied by a creature with those additional types having dealt combat damage to a player.