any of five species of small seabirds of the sub-Antarctic regions that constitute the family Pelecanoididae (order Procellariiformes). Although their nearest relatives are the storm petrels, shearwaters, and albatrosses, diving petrels differ from these long-winged forms and instead resemble the smaller auks of the Northern Hemisphere, a classic example of convergent evolution. Like the auks, black-and-white diving petrels are short-winged and heavy-bodied and use their wings for propulsion underwater. The smallest and most widespread is the common diving petrel (Pelecanoides urinatrix), about 16 cm (6.5 inches) long; the largest is the Peruvian diving petrel (P. garnotii), about 25 cm long, restricted to the west coast of South America from about 6° to 37° S.