EVERYDAY SCIENCE

Detailed explanation-1: -The monotremes are the only mammals that lay eggs. The marsupials are found today only in Australia and surrounding islands, North America, and South America. Their earliest appearance in the fossil record is in the Cretaceous of North and South America, and fossils are known from all continental landmasses.

Detailed explanation-2: -One line of thinking is that marsupial diversity is greater in Australia than in South America because there were no terrestrial placental mammals to compete with marsupials in ancient Australia. Kangaroos are the only large mammal to use hopping as their primary form of locomotion.

Detailed explanation-3: -Australia and Antarctica gradually moved away from South America and both continents became isolated. Marsupial mammals were free to evolve in isolation, and evolution produced the characteristics found in present day Australian mammals.

Detailed explanation-4: -There are over 330 species of marsupials. Around two-thirds of them live in Australia. The other third live mostly in South America, where some interesting ones include the flipper-wearing yapok, bare-tailed woolly opossum, and don’t get too excited, but there’s also the gray four-eyed opossum.

Detailed explanation-5: -The platypus Ornithorhynchus anatinus, is a unique Australian species. Along with echidnas, platypus are grouped in a separate order of mammals known as monotremes, which are distinguished from all other mammals because they lay eggs. The platypus and echidna have both survived by occupying ecological niches.