Australian Plate south, is now being torn apart along the transform boundary marked by the Alpine Fault. South of New Zealand the boundary becomes a transitional transform-convergent boundary, the Macquarie Fault Zone, where the Australian Plate is beginning to subduct under the Pacific Plate along the Puysegur Trench. Extending southwest of this trench is the Macquarie Ridge. The southerly side is a divergent boundary with the Antarctic Plate called the Southeast Indian Ridge (SEIR). The subducting boundary through Indonesia is not parallel to the biogeographical Wallace line that separates the indigenous fauna of Asia from that of Australasia. The eastern islands of
Mainland Southeast Asia Thailand, Laos, Cambodia and Vietnam). To the south it forms the Malay Peninsula, on which are located Southern Thailand and Peninsular Malaysia; the latter is variably considered part of Mainland Southeast Asia or separately as part of Maritime Southeast Asia. Mainland Southeast Asia contrasts with Maritime Southeast Asia, mainly through the division of largely land-based lifestyles in Indochina and the sea-based lifestyles of the Malay and Philippine archipelagos, as well as the dividing line between the Austroasiatic, Tai–Kadai, Sino-Tibetan languages (spoken in Mainland Southeast Asia) and Austronesian languages (spoken in Maritime Southeast Asia). The countries of mainland Southeast Asia received