Wallacea

Wallacea /wɒˈleɪsiə/ is a biogeographical designation for a group of mainly Indonesian islands separated by deep-water straits from the Asian and Australian continental shelves.

[1] Wallacea is defined as the series of islands stretching between the two continental shelves of Sunda and Sahul, but excluding the Philippines.

The islands of Sundaland to the west of the line, including Sumatra, Java, Bali, and Borneo, share a mammal fauna similar to that of East Asia, which includes tigers, rhinoceros, and apes; whereas the mammal fauna of Lombok and areas extending eastwards are mostly populated by marsupials and birds similar to those in Australasia.

[citation needed] Similarly, Australia and New Guinea to the east are linked by a shallow continental shelf, and were linked by a land bridge during the ice ages, forming a single continent that scientists variously call Australia-New Guinea, Meganesia, Papualand, or Sahul.

Consequently, Australia, New Guinea, and the Aru Islands share many marsupial mammals, land birds, and freshwater fish that are not found in Wallacea.

There is extensive autochthonous speciation and proportionately large numbers of endemics; the area is an important contributor to the overall mega-biodiversity of the Indonesian Archipelago.

Smaller mammals, including some carnivorans (such as civets), marsupials (such as the cuscus), primates and rodents are common throughout the region.

Australian Early-Middle Pliocene rodent fossils have been found in Chinchilla Sands and Bluffs Down in Queensland, but a mix of ancestral and derived traits suggest murid rodents made it to Australia earlier, maybe in the Miocene, over a forested archipelago, i.e. Wallacea, and evolved in Australia in isolation.

[8] Australia's rodents make up much of the continent's placental mammal fauna and include various species from stick-nest rats to hopping mice.