Science Daily had the most amazing article out in May 2013 about comb jellies and the tree of life. A lot of effort has gone into drawing the tree of life with its branches that show how each life split off in time; yes, we are there too close to the chimps and a little further away from the gorillas.
Sponges were supposed to be the bottom, nothing lower. Sponges are almost not alive but surprise, surprise! they are not the bottom of the tree of life. Comb jellies, with muscles, nerves, and a brain! were discovered to be older. Scientists are baffled! Does this mean that life began twice? Heresy!
Going back to the Edicaran fauna 600 million years ago, those strange creatures of the Burgess Shale, of which we see nothing but fossils, one is forced to ask: did the comb jellies originate in the Edicaran explosion of life form and its equally rapid demise?