Modern Koalas Not Descended From Prehistoric Giant Species

A Discovery News article, via ABC Science, explains findings that suggest that the modern day koalas of Australia do not appear to be evolutionary ancestors to prehistoric giant koalas.  I was not previously aware that there were once giant koalas on Australia, but supposedly there were.  The species is called Phascolarctos stirtoni and lived during the Pleistocene.  Supposedly they could gow to weigh as much as 30 Kg.  Something about giant koalas strikes me as somewhat disturbing, especially because I have read that modern koalas are quite territorial and not really all that friendly.  This findings have led to greater speculation about what happened to much of Australia’s prehistoric megafauna.