Cephalopods - octopus and squid - are pretty strange. But their ancestor was stranger. A half-billion years ago, a kite-shaped animal with two long tentacles and big eyes on stalks cruised the ancient seas. Its name was Nectocaris pteryx.
UPDATE: Dr. Charles Paxton has written in to note that it may be premature to grant Nectocaris the honored position of common ancestor to the cephalopods. He comments, "...I can see it looks like a larval teuthid but surely it should have a radula even if no beak or shell? [ED: the radula is the tonguelike abrasive structure all cephalopods use in feeding.] Why wouldn't that be preserved given the preservation of the other soft tissue? The authors argue the mouthparts are not well preserved. Do they have an objective way of knowing that or is it a convenient way to explain away the absence of a beak and radula in their putative cephalopod? The cephalopod affiliation is further reliant on identification of a "funnel" and no formal phylogenetic reconstruction is presented in the sense of comparison of traits using an algorithm."
In other words: Like a lot of claims made in science, the one made for Nectocaris is not a certainty. Future fossils may confirm the hypothesis or refute it. Science at work.
Thanks to Charles for writing in.