Thirioux’s Grey Parrot (Palaeornis bensoni)
Thirioux’s Grey Parrot, also known as Mauritius Grey Parrot, is an extinct member of one of the most remarkable radiations of birds that we currently know of and which repeatedly settled the Mascarene Islands to give rise to new, endemic forms, this happened several times, leading to the formation of several endemic forms.
The species was originally described on the basis of subfossil bones that were recovered from a cave in the mountains of Mauritius, it was then described as being a close relative of the likewise extinct Broad-billed Parrot (Lophopsittacus mauritianus (Owen)).
In 2007, however, the remains were reinvestigated and recognized to be very similar to the bones of the Alexandrine Parakeet (Psittacula eupatria (L.)) and thus were assigned to the genus Psittacula.
A study in 2019 found out that the genus Psittacula is polyphyletic, that means that this genus actually contains several distinct clades and should be split into several genera. This species was unfortunately not included in the study, however, being skeletally similar to the Alexandrine Parakeet, I decided to tentatively include it in the genus Palaeornis. 
 Michael P. Braun; Thomas Datzmann, Thomas Arndt; Matthias Reinschmidt; Heinz Schnittker; Norbert Bahr; Hedwig Sauer-Günth; Michael Wink: A molecular phylogeny of the genus Psittacula sensu lato (Aves: Psittaciformes: Psittacidae: Psittacula, Psittinus, Tanygnathus, †Mascarinus) with taxonomic implications. Zootaxa 4563(3): 547-562. 2019