Marsupials had evolved and been living in Gondwana after the supercontinent Pangea split up. Gondwana was composed of what is now Africa, Australia, South America, Madagascar, New Zealand, Arabia, India and Antarctica.
You might be asking yourself why Australia is the only continent known for marsupials if Gondwana consisted of many now known continents? Well, Australia was the prime location for the development of marsupials because it lacked many large predators and placental mammals. With nothing to really outcompete the existing marsupials that had been living in that area after the split from Gondwana: The marsupials flourished with adaptive radiation.
What's interesting about this adaptive radiation is that marsupials evolved in many of the same ways that our placental mammals have in the America's and elsewhere. This similar evolution is known as convergent evolution, and I find it truly amazing that despite being in completely different locations; we see many of the same morphologies.
The image above shows some examples of this convergent evolution. When I stop to think about how this convergent evolution took place, I find myself asking what exactly is it about certain terrains and our food chain that causes these morphologies to be so similar? Perhaps a lot of this adaptive radiation occurred with the common ancestor to both subclasses of mammals, and that these morphologies just kept getting passed down up to Australia's separation and then elaborated on when the separation occurred? If anyone has any other ideas or wants to add their thoughts then please do so!
Post by Mitchel Logan (B)