Papua New Guinea notable feature in common for the two landmasses is the existence of several species of marsupial mammals, including some kangaroos and possums, which are not found elsewhere. Papua New Guinea is a megadiverse country. Many of the other islands within PNG territory, including New Britain, New Ireland, Bougainville, the Admiralty Islands, the Trobriand Islands, and the Louisiade Archipelago, were never linked to New Guinea by land bridges. As a consequence, they have their own flora and fauna; in particular, they lack many of the land mammals and flightless birds that are common to New Guinea and Australia. Australia and New
Fauna of New Guinea ago. As it drifted north, New Guinea moved into the tropics. Throughout New Guinea's geological history there have been many land connections with Australia. These have occurred during glaciations in various ice ages. Four occurred during the Pleistocene; the last of which was severed 10,000 years ago. At this time, a number species existed on both land masses, and many plants and animals thus crossed from Australia to New Guinea and vice versa. Many later became isolated as the connection ended, then further evolving to the new environment and becoming distinct species. However, this Australia-New Guinea mixing occurred among a