The original “penguin” was in fact the late great auk (Pinguinus impennis), once found in vast numbers around northern shores of the Atlantic.
Although no relation to southern hemisphere penguins, it was very similar in appearance, and filled much the same ecological niche as penguins, particularly the king penguins of the subantarctic region.
via Ian Bicking's G+ post: https://plus.google.com/+IanBicking/posts/NDDNYauEHpm