Maybe, Kendall; but it is an adjective in apposition, and you err in callling it an adverb. The fact is that, even if you fiond the second uneuphonious [fort some obscure reason of your own, 'important' is an adjective whose derived adverb is 'importantly'.

"This is a very interesting discovery," he announced importantly.

You couldn't say "He announced important", could you; because it isn't an adverb for all your saying. And if, as you would seem likely to suggest, you would substitute, "He said in an important manner", you would simply have substituted an adverbial phrase using the adjective, which would strike me as otiose use of superfluous words.

~M~