True owls have colonised all of the main island groups in the Indian Ocean. The oceanic island species comprise the genus Otus and it is from this genus that the endemic Mascarene genus Mascarenotus was derive). The Mascarene species were characterised by large size and long legs, presumably adaptations for reptile/small bird predation. The Mascarene owls are known from descriptions, one drawing and very few skeletal elements.
The Mauritian species Mascarenotus sauzieri was a large white-faced, horned owl with bare tarsi. A drawing by the artist Jossigny is the only known illustration of the genus. One specimen was described in detail by Desjardins in 1837, while a few others were reported around the same time. George Clark in 1859 stated that they were now extinct after being formerly plentiful. A second species Strix newtoni was described, based on smaller tarsometatarsi, but these elements fit well within the range of M. sauzieri individual variation.
Owls were never reported historically on Réunion but bone remains confirm that a similar, possibly slightly smaller species M. grucheti once existed there. A third species M. murivorus was mentioned on Rodrigues. It was described as a small brown owl that fed on lizards and birds and lived almost exclusively in trees. Pingré in 1761 never reported them so they presumably disappeared in the mid 1700s.