Aldabra is a breeding ground for the hawksbill sea turtle ("Eretmochelys imbricata") and green sea turtle ("Chelonia mydas"). Aldabra has one of the largest populations of nesting green turtles in the Western Indian Ocean. Aldabra has a large population of the world's largest terrestrial arthropod, the coconut crab ("Birgus latro"); and hosts the white-throated rail, the only surviving flightless rail species in the Indian Ocean. Sharks, manta rays, barracuda can be found in the seas surrounding the island. During the Pleistocene the dominant land predator was the crocodilian "Aldabrachampsus" which is now extinct. Three extant species of lizards occur, the skink "Cryptoblepharus boutonii" and the geckos "Phelsuma abbotti" and "Hemidactylus" "mercatorius". Pleistocene fossils also indicate the former presence of an "Oplurus" iguana and other skink and gecko species. There are three endemic species of bat from Aldabra: "Paratriaenops pauliani", "Chaerephon pusilla" and the Aldabra flying fox ("Pteropus aldabrensis"), as well as the more widely distributed Mauritian tomb bat ("Taphozous mauritianus"). There are 1,000 species of insects, many of them endemic. Many species of butterflies also flutter around Aldabra.