 Long thought to be related to frigatebirds, cormorants, tropicbirds, and gannets and boobies, pelicans instead are now known to be most closely related to the shoebill and hamerkop, and are placed in the order Pelecaniformes.Ibises, spoonbills, herons, and bitterns have been classified in the same order.Fossil evidence of pelicans dates back at least 30 million years to the remains of a beak very similar to that of modern species recovered from Oligocene strata in France.