They get their name from marsupium – the pouch. Their young are born so early that they need to complete their embryonic development while nursing, which in most species occurs in their mother’s pouch. A red kangaroo for example is about the size of a honeybee when it is born only 33 days after fertilisation. Here are some facts about marsupial mammals, their origins and convergent evolution of species like marsupial mole and marsupial mouse.
Marsupials and Continental Drift Marsupials are the largest and most successful group of native mammals in Australia. The reason for this unique fauna is Australia’s long isolation from other continents. When the super-continent Pangaea broke up about 200 million years ago, reptiles still ruled the world. Dinosaurs were very successful - although small mammals existed, they never got a chance to dominate the Animal Kingdom. Once the dinosaurs got extinct by what is believed to be a sudden climate change caused by a meteorite or a volcano (theories vary), Pangaea had already drifted apart to form two continents: the northern Laurasia, and the southern Gondwana. All of a sudden mammals got the chance to develop into many different species, and it so happened that on Laurasia, they developed into placental animals, and on Gondwana they developed into marsupials.
Marsupials and Placental Animals When Gondwana broke up, India got attached to Asia, Africa to Middle East and South America to North America. Marsupial and placental animals were joined, and marsupials got extinct. Australia was never connected to any other continent, and here they survived. South America still has a few species of what they call opossums, but generally placentals were more successful, or perhaps because in placental world there were more large predators (there are no large carnivorous animals in Australia), marsupials didn’t survive.
Marsupial Animals and Convergent Evolution It is interesting how placental and marsupial animals developed in separation. Animals that fill similar niches in both hemispheres look remarkably similar, although they have developed totally independent to each other. Look at Australian animals: a marsupial mole has got features exactly like a mole of Northern Hemisphere, a marsupial mouse looks like a mouse of Northern Hemisphere, and a sugar glider looks like a flying squirrel. Just because they lived in similar environments and used similar strategies they developed similar features in what is called convergent evolution.
NOTE: This website is written in British English, which is the English we use in Australia. You will find words like "traveller", "harbour" and "realise", and they are all correct in the language used in Australia.
