Here we have a mammalian type of animal found in Tasmania whose remains have been found everywhere else in the world, every other continent including Antarctica. So it is possible that other mammalian types of animals may have been around at the time, or evolved from them everywhere.
http://www.themercury.com.au/article/20 ... -news.html
Does tend to leave open some intriguing questions about what was and is. Just goes to show that science does not know everything and is finding unknown life forms all the time.