Marsupials are a distinctive group of mammals characterized by their unique mode of reproduction and development, setting them apart from placental mammals. They belong to the infraclass Metatheria and are primarily distributed in Australia, New Guinea, and parts of the Americas, especially South America. Common examples include kangaroos, wallabies, koalas, wombats, opossums, bandicoots, and Tasmanian devils. Their evolutionary history indicates an early divergence from the placental mammal lineage, followed by extensive adaptive radiation, particularly in the Australian continent where placental mammals were largely absent. One of the most defining features of marsupials is their reproductive strategy. Gestation period in marsupials is extremely short, often lasting only a few days to weeks. As a result, the young are born at a highly immature, altricial stage. These tiny, underdeveloped newborns must