Fossils of true geese are hard to assign to genus; all that can be said is that their fossil record, particularly in North America, is dense and comprehensively documents many different species of true geese that have been around since about 10 million years ago in the Miocene. The aptly named "Anser atavus" (meaning "progenitor goose") from some 12 million years ago had even more plesiomorphies in common with swans. In addition, some goose-like birds are known from subfossil remains found on the Hawaiian Islands.