According to my new book on bears (Bears, Bears, Bears), the spectacled bear is the only remaining descendant of the short-faced bears, which explains why it has the shortest muzzle among the bear family. I hadn't realized there were any descendants of the short-faces remaining. Which is why books on bears are so valuable- you should all go buy some today.
Since I can't show you my book, here is a website with the same info. And I like this drawing of what a short-faced bear might have looked like, while this scary guy comes from the BBC website.