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 as with Australia, are very diverse with 46 species, a seventh of the world's total. The forty-five species of pigeons, including the three crowned-pigeons, the largest pigeons in the world, are a sixth of the world's total. The passerines display the greatest amount of diversity with over 33 families within New Guinea. The passerines of New Guinea are mostly small, often colourful birds which mostly inhabit the forested regions. The best-known family in New Guinea is the Paradisaeidae, one of three families there known collectively as birds-of-paradise. Many species show extravagant sexual dimorphism. The males can be ornamented with bright,