How marsupials got to Australia

It is well known that Australia is home to many marsupials, but what I did not know until recently is that marsupials arrived from South America crossing Antarctica. As Pangea (200 mya) was breaking up around 150-100 mya, marsupials seem to have been plentiful in South America and used then-unfrozen Antarctica as a bridge to get to Australia. Placental mammals still had not reached Australia by the time it broke off from all other continents, so marsupials never had to compete with placentals.

Today there are actually still over 100 types of marsupials in the Americas, largely possums.

See the graphic below off wikipedia. http://en.wikipedia.org/wiki/Marsupial#Evolution

And it is strange that on a continent with such unusual species, humans would raise millions of cows, sheep, and pigs; but then again that's true in South America as well. And they do have kangaroo farms and eat kangaroo meat.

Great article by Bob Strauss
http://dinosaurs.about.com/od/otherprehistoriclife/fl/Marsupial-Evolution.htm