Parrots, also known as psittacines (), are the 402 species of birds that make up the order Psittaciformes, found in most tropical and subtropical regions, of which 387 are extant. The order is subdivided into three superfamilies: the Psittacoidea ("true" parrots), the Cacatuoidea (cockatoos), and the Strigopoidea (New Zealand parrots). Parrots have a generally pantropical distribution with several species inhabiting temperate regions in the Southern Hemisphere as well. The greatest diversity of parrots is in South America and Australasia. The Cacatuoidea are quite distinct, having a movable head crest, a different arrangement of the carotid arteries, a gall bladder, differences in the skull bones, and lack the Dyck texture feathers that—in the Psittacoidea—scatter light to produce the vibrant colours of so many parrots. Lorikeets were previously regarded as a family, Loriidae, but are now considered a tribe (Loriini) within the subfamily Loriinae, family Psittaculidae. Some species, such as the Puerto Rican amazon (Amazona vittata) have had a population bottleneck (in this case reduced to 13 individuals in 1975) and subsequently have low genetic variability and low reproductive success, leading to complications with conservation. No consensus existed regarding the taxonomy of Psittaciformes until recently. The placement of the Strigopoidea species has been variable in the past. They were once considered part of the Psittacoidea, but recent 21st-century studies place this group of New Zealand species as their own superfamily next to the Cacatuoidea and remaining members of the Psittacoidea. Many studies have confirmed the unique placement of this group at the base of the parrot tree. Most authors now recognize this group as a separate taxon containing two families: Nestoridae and Strigopidae. Conversely, the relationships among various cockatoo genera are largely resolved. Conventions Conservation status codes listed follow the International Union for Conservation of Nature (IUCN) Red List of Threatened Species. Range maps are provided wherever possible; if a range map is not available, a description of the bird's range is provided. Ranges are based on the IUCN red list for that species unless otherwise noted. All extinct species listed went extinct after 1500 CE (recently extinct), and are indicated by a dagger symbol "†". Classification The order Psittaciformes consists of 387 extant species belonging to 87 genera. The following classification is based on the most recent proposals as of 2012. Superfamily Psittacoidea: true parrots Family Psittacidae Subfamily Psittacinae: two African genera, Psittacus and Poicephalus Subfamily Arinae Tribe Arini: eighteen genera