Psittacula

Genetic evidence has found that the genus Psittacula is likely paraphyletic; for example, genetic analysis has supported merging short-tailed parrots of the genus Tanygnathus, Psittinus, and the extinct Mascarinus with Psittacula.[7] A revised classification was proposed by Michael Braun and coworkers in 2019 that splits the genus Psittacula into multiple monophyletic genera in order to preserve Tanygnathus, Psittinus, and Mascarinus as distinct genera. After the proposed split, the only remaining species in Psittacula sensu stricto are P. derbiana, P. caniceps, and P. alexandri.[6] This is also the taxonomic system followed by the IUCN Red List and BirdLife International. The list of split or monophyletic genera and species (and any of their allied species) is displayed below:

• Genus Himalayapsitta
  • Plum-headed parakeet, Himalayapsitta cyanocephala
  • Grey-headed parakeet, Himalayapsitta finschii
  • Slaty-headed parakeet, Himalayapsitta himalayana
  • Blossom-headed parakeet, Himalayapsitta roseata
• Genus Nicopsitta
  • Blue-winged parakeet, Nicopsitta columboides
  • Layard's parakeet, Nicopsitta calthrapae
• Genus Belocercus
  • Long-tailed parakeet, Belocercus longicauda
• Genus Psittacula
  • Red-breasted parakeet, Psittacula alexandri
  • Lord Derby's parakeet, Psittacula derbiana
  • Nicobar parakeet, Psittacula caniceps
• Genus Palaeornis
  • Alexandrine parakeet, Palaeornis eupatria
  • †Seychelles parakeet, Palaeornis wardi
• Genus Alexandrinus
  • Rose-ringed parakeet, Alexandrinus krameri
  • †Newton's parakeet, Alexandrinus exsul
  • Echo parakeet, Alexandrinus (eques) echo
• Genus Tanygnathus
  • Great-billed parrot, Tanygnathus megalorynchos
  • Blue-naped parrot, Tanygnathus lucionensis
  • Blue-backed parrot, Tanygnathus sumatranus
  • Black-lored parrot, Tanygnathus gramineus
• Genus Psittinus
  • Blue-rumped parrot, Psittinus cyanurus
  • Simeulue parrot, Psittinus abbotti
• Genus †Mascarinus
  • †Mascarene parrot, Mascarinus mascarin
• Genus †Lophopsittacus
  • †Mauritius grey parrot, Lophopsittacus bensoni

The extinct Mascarene grey parrot (P. bensoni) was not sampled in the study and has not been reclassified to Psittacula sensu lato by the IUCN or BirdLife, so it is still classified in Lophopsittacus under this taxonomy and with the common name Mauritius grey parrot.[8] The Nicobar parrot(P. caniceps) was also not sampled but kept in Psittacula by the authorities that incorporated this taxonomy.[9]

The study has also found that the rose-ringed and red-breasted parrots are likely paraphyletic species themselves, and thus need to be split into multiple species.[6]

The Rothschild's or intermediate parakeet P. intermedia, found in northern India, was formerly considered a mystery, as only very few specimens were known. It has since been demonstrated to be a hybrid between the slaty-headed parrot P. himalayana and the plum-headed parrot P. cyanocephala.[10][11]

The taxonomy of the Réunion parakeet P. eques is also confusing. Extinct since 1770, little evidence even exists of the bird's existence. A study skin had been discovered at the Royal Museum of Scotland, explicitly referencing a book description of the Réunion birds. It is known from other descriptions, as well as illustrations of which it is unknown whether they were drawn from live or stuffed specimens. This may be the only material proof of these birds' existence. Taxonomists are unsure if the birds were a distinct species, or conspecific with the echo parakeet, although genetic analysis supports it being a subspecies of the echo parakeet.