Albatrosses, of the biological family Diomedeidae, are large seabirds allied to the procellariids, storm petrels and diving petrels in the order Procellariiformes (the tubenoses). They range widely in the Southern Ocean and the North Pacific. They are absent from the North Atlantic, although fossil remains show they once occurred there and occasional vagrants are found. Albatrosses are among the largest of flying birds, and the great albatrosses (genus Diomedea) have the largest wingspans of any extant birds, reaching up to 3.7 metres (12 feet). The albatrosses are usually regarded as falling into four genera, but there is disagreement over the number of species.