Holy fuck, there's an Ediacaran chordate!
More on the Panda's Thumb, including:
[Y]ou can see grooves that record the record the muscle bands [...] there are now 18 of these fossils described, preserved in every possible orientation, so they know it is not a frond animal, but a fossil of the first chordate.
Via Pharyngula.
"Holy Fuck"? I'm going to auction a semi ingested cheese sandwich on ebay on which you can CLEARLY see the image of an Ascidia virginea that has recently reproduced (asexually of course). Any bidders?
The real mystery is how Ediacaran Chordates devolved into IDer's.
You named it, there's no mystery; they're adult ascidians, reduced to little more than a bag and a siphon and permanently clinging to some useless piece of substrate. We're their neotenous larvae, grown up from free-swimming cephalochordates into full-blown sapience.