Nectocaris pteryx, one of Stephen Jay Gould's "weird wonders" from the Burgess Shale may have found a home in the Family Tree O' Life:
Long thought perhaps a shrimp ancestor, a newly-found fossil reveals the creature was instead an ancestral cephalopod, albeit with two-tentacles instead of eight seen in modern octopi. The find, "extends the cephalopods' fossil record by over 30 million years, and indicates that primitive cephalopods lacked a mineralized shell, were hyperbenthic (seabed-dwelling), and were presumably carnivorous," says the study.
The giveaway? A funnel under its eyes, used to jet around like modern cephalopods.
Note that, with only two tentacles, Nectocaris would not have been a favorite of Pre-Cambrian Sushi joints.
PS: more info and a few more pictures here.