Procellariformes are an ancient order of birds. The fossil record goes back at least 36 million years. These earliest known fossils are of birds very similar to present day species suggesting that the Petrels as a group were already well separated from the main line of avian development. This and mitochondrial studies suggest that Petrels of one sort or another may have been flying across antediluvian seas as much as 50-55 million years ago. They are rarest in tropical waters.
Most species however nest on remote islands or inhospitable sea cliffs.
At the other extreme is Wilson's Storm Petrel which some ornithologists estimate is one of the most numerous birds in the world. Some scientists think that some species of the smaller Prions and diving Petrels may be even more numerous. As well as a large range in distribution and population biology, the Procellariiformes have one of, if not the greatest range in size of any order of birds. This means that the largest Procellariiform is 8.6 times as long, 11.25 times as large in the wingspan and 274 times as heavy as the smallest. This is a good example of the fact that while area increases approximately to the squared power of length, mass or volume increases with the to the cubed power of length.