The Boat-Billed Heron (Cochlearius cochlearius) is a somewhat strange member of the family Ardeidae, although it was previously placed in its own family, the Cochlearidae. As you can tell from the above photograph taken at the "Aquatic Bird House" at the Bronx Zoo, the bill of this type of bird is oddly shaped, making it somewhat difficult to place among other living herons.
But apart from the oversized beak, it's a fairly standard night heron (Nycticoracini).
I remeber when my bird books used to list it as a separate family. Even then it seemed a little over-rated to me.
The boat-billed heron, an oddity indeed! (Even if it is merely a specialised Night-Heron) Believe it or not, I once came across one at a shop in Belgium where birds are sold for aviculture. Eventhough this particular shop (though it's rather big for a shop) has had other oddities (eagle owls, crowned cranes, a Palm Vulture(!), jacanas and rheas amongst others) the boat-billed heron struck me as particularly unusual, if only because I'd never seen one before or seen one since. Its concrete and empty enclosure failed to do it much justice, however. I can only hope it was soon bought and is now residing in more pleasant surroundings.